Tony Tony Chopper/History

No Disease is Incurable
Chopper was originally a reindeer with the slight oddity of a blue nose, which caused other reindeer to treat him as an outcast (always making him follow the herd from far back). However, when the young reindeer ate the Hito Hito no Mi, he was even more ostracized from his herd (and with the increase in intelligence granted by the fruit, now acutely aware of it) and struck out on his own. Unfortunately for Chopper, his attempts at communicating with the humans on Drum Island proved disastrous, he was shot by villagers who mistook him for the Abominable Snowman.

Luckily, though, he was rescued by the quack Dr. Hiluluk, who named him and took him in as his friend and "assistant". Although his deeds were of dubious medical value, Dr. Hiluluk became Chopper's role-model. Hiluluk taught Chopper his philosophy on life (that all diseases could be cured) and his strong faith in the Jolly Roger as a symbol of strength against all odds. The two went from house to house, administering their "cures" in a country where all doctors not sanctioned by King Wapol were banned.

When Hiluluk's health took a turn for the worse, Chopper found himself left out in the cold once again as the old man did not want Chopper to watch him die. But once Chopper found out what was going on, he was determined to find something to cure his mentor, his one and only friend. He soon found what he was looking for: a special kind of mushroom with skull-and-crossbones prominently displayed in the medical book, unaware of what that sign meant medically due to Hiluluk's praising of pirates and the jolly roger. Remembering what he overheard by some villagers that a "certain" type of mushroom can heal every illness, Chopper steals Hiluluk's favorite medical book to find the miracle mushroom. Chopper's arduous journey was a success, even though he risked his life and suffered many injuries, such as a broken left horn.

Hiluluk overwhelmed with tears of gratitude, ate the mushroom to show his love and appreciation to Chopper,(despite knowing that it would end his life) but Chopper would later find out from Dr. Kureha that he had given Dr. Hiluluk a fatal dose of poison. But Hiluluk was not to live much longer anyway. Declaring that he had a wonderful life (in the 4kids dub he declares he is a doctor)and after thanking Chopper, he committed suicide by blowing himself up outside of Drum Castle (before being killed by the poison, for Chopper's sake). Chopper, who had arrived to try and save him, was so upset over Hiluluk's death that and so angry that Wapol was making fun of it that then tried to attack him. Dalton, who had heard Hiluluk's last words and realised that the monster he called his son was trying to attack Wapol he then stopped him. He then, with tears in his eyes told him that he apologized for those who mocked Hiluluk death but that he could not beat Wapol if he could not beat him.

As for Hiluluk's last wish, Dr. Kureha (the last remaining doctor not owned by King Wapol) took Chopper in and taught him "real" medicine for the next 6 years. Chopper worked as hard as he could, in order to become a doctor like his idol, Hiluluk.

Fall of the Drum Kingdom
However, Chopper's isolated life in Drum Castle (which he and Dr. Kureha annexed after King Wapol fled) would one day come to an end with the arrival of Monkey D. Luffy and his pirate crew. Chopper, naturally distrustful of humans, was not pleased, especially given Luffy and Sanji's desire to cook and eat him.

But when Chopper showed both his medical capabilities and his skills in battle against the returned forces of King Wapol, Luffy offered (forced) him the (as-yet unfilled) position of Ship's Doctor in his crew. While Chopper was at first unwilling to leave, he remembered Dr. Hiluluk wishing Chopper to sail seas to see the world on his own and with his desire to broaden his medical horizons, he decides to join Luffy and his crew.

Fleeing the castle with the Straw Hat Pirates, Chopper was given a send-off of gigantic proportions: Kureha had turned the snow into sakura blossoms, the very same that Hiluluk had researched over 30 years that would one day, cure the people of Drum of their "sickness of the heart," passed to Dr. Kureha as one of his last request before death. Overcome with tears, Chopper made a fond farewell to his birthplace and mentors, setting out to sea for the first time in his life.

War in Alabasta
The crew saw a Sea Cat as they neared Alabasta. Starving for food, they try to capture it but Vivi stop them since it was considered a sacred animal. As they pass through some steam from an underwater volcano, Luffy and Usopp caught an okama while fishing. As they waited for his crew to catch up, he entertains them with his Devil Fruit ability to copy other people's appearances, one of which was Vivi's father. When the man's crew caught up, he was revealed to be Mr. 2 Bon Kurei of Baroque Works. Knowing his abilities, they made an 'X' mark on their left arms to know when he was posing as one of them.

The crew landed in Nanohana where they encounter Smoker and Tashigi. A powerful pirate named Portgas D. Ace appears, and is revealed to be Luffy's older brother. Ace fights Smoker while the Straw Hats run for their ship. Ace catches up to them and gave Luffy a Vivre Card before departing. They docked their ship near the once 'green city' of Erumalu where they see the extent of the country's suffering as Vivi explained how Baroque Works was using Dance Powder to cause it. After tackling some of the dangers in the desert, they reach Yuba where they meet Toto, a friend of the royal family. They find out that the Rebel Army has moved out of Yuba and headed to Katorea, and the rebel leader Kohza, Toto's son and Vivi's childhood friend, is determined to attack.

The crew travels to the city of Rainbase to take down Crocodile and Baroque Works, but run afoul of Smoker and Tashigi. Luffy, Zoro, Nami, Usopp, and Smoker are trapped by Crocodile. Chopper distracts Crocodile while Sanji frees the rest of the crew, but find themselves trapped yet again. After escaping from Rain Dinners, Usopp and the crew together with Vivi crossed the desert to Alubarna, where the final battle will take place.

Crocodile, however, manages to catch Luffy, beginning the first round of their battle. The crew, excluding Luffy, proceeded to the Alubarna. As they reach the destination, they split up to distract the Baroque Works agents to engage their battle separately. At first Chopper was paired with Sanji when the two were pursed by Mr. 4 and Miss Merry Christmas, until Sanji left to check up on Usopp and Chopper had to fight by himself for a short while until Usopp came to assist him. The battle of Usopp and Chopper vs. the Mr. 4 team then began.

Things look hopeless for Usopp and Chopper as they continue to suffer from every attack that the Mr. 4 team makes. When Miss Merry Christmas tells them that Luffy is dead, Usopp refused to believe it, claiming that Luffy will become the next Pirate King. When she laughs at this, Usopp tells Chopper that a real man never lets his friend's dreams be laughed at and must fight for it no matter what. Albeit severely beaten and bruised, Usopp and Chopper finally defeated the Mr. 4 team.

Later, the Straw Hats hurried to locate the bomb before it goes off. Vivi figured out where the bomb was, and had Usopp call the Straw Hats together with a flare. She found it inside of the clock tower, but the Mr. 7 pair of Baroque Works were there. Vivi defeats them but realized the bomb cannot be stopped so easily. It has a timer, and right before it blows up, Pell shows up and takes it into the atmosphere, where he sacrifices himself to save Alubarna.

The Rebel and Royal armies continued to fight even after the bomb went off. It wasn't until it rained and Crocodile was revealed to be one behind the drought that they stopped. Tashigi and Smoker both were rewarded for taking on Crocodile, but neither one of them believed it was right since the Straw Hat pirates did all the work. Luffy rescued Nico Robin and Cobra from the collapsing tomb where he fought and defeated Crocodile. He was then brought to the palace to rest. When he awakened, a banquet is thrown for the pirates. They were then invited to enjoy the hotspring steam-room inside the palace.

Later that night, Mr. 2 Bon Kurei contacted them, telling them he prevented their ship from being taken by the Marines. The next day, the day of her speech, Vivi was to make a decision on whether or not she will stay on the crew. Meanwhile, Bon Kurei and his crew helped the Straw Hats escape from Hina so they could get to Vivi, who declined joining them for the sake of her country. Regardless, they all showed their 'X' mark to signify that they will still consider her as one of them. After escaping from the Marines, Nico Robin (Ms. All Sunday) appears from inside of the Straw Hats ship. She manages to persuade the crew to let her join since she had nowhere else to go.

Rumble in Jaya
Nami's Log Pose begins to point to the sky, after that, a big ship falls from sky and the crew finds a map in of an island named 'Skypiea' on a 200-year-old ship. They compete with the monkey-like Masira's salvage crew while they search for more clues on how to get there. The Straw Hats decide to go to Jaya island to look for information on Skypiea. The Straw Hats meet with Montblanc Cricket on another part of Jaya; Cricket is a descendant of Montblanc Noland, an infamous "liar" who told of a gold city on Jaya, and Cricket was outcast for looking for artifacts of the gold city. He may be the only person who knows how to get to Skypiea.

Cricket explains how the Straw Hats can ride a dangerous vertical current called the Knock Up Stream to get to Skypiea. However, they first have to catch a South Bird to point them toward the point where the stream will erupt from the ocean. While the Straw Hats are looking for a South Bird, Bellamy and his crew attack Cricket's house, and steal the gold artifacts he'd collected over the years from his salvage work. When the Straw Hats return and see what happened, Luffy decides to take a side trip back to Mock Town. The Going Merry is refitted by Masira and Shoujou to be more flight capable, and the Straw Hats catch a ride on the Knock Up Stream for Skypiea.

Adventure in a Sky Island and Taking Down a God
They start from entering the Gate of Heaven. First they have been recommended by an old woman to pay their extol, but even they have not pay the old woman let their pass. As they carried by a sky shrimp, they landed on a place that's surrounded by clouds. They met their Conis, a Skypiean. As their conversation continues about the waver, the White Berets interrupt them and labeling them as a criminal of illegal entrants. As Chopper along with Zoro, Nami and Robin aboard the ship, the shrimp suddenly carried them, Zoro tried to kill it but there's something behind. The shrimp leave them in the Sacrificial Altar. Zoro, Nami and Robin explored the land and leave Chopper as to guard the ship.

As he guarded the ship Shura, one of the priest suddenly appeared to eliminate him. He fight Shura with his ability but finds himself no match for the priest. He whistled the whistle to call Gan Fall. As Gan Fall appeared, they fight each other but in the end, Gan Fall is defeated. Gan Fall fell into the water surrounding the altar and Chopper jumped in to save him but cannot swim. Both Gan Fall and Chopper were saved from drowning by the giant south birds. Chopper is then told by the birds that Gan Fall is the former god. As the crew reunited, he is seen healing Gan Fall. They spent a night on the ship to regain more energy.

The next morning, Chopper explores the island together with Luffy, Zoro, and Robin to search for the gold but a giant python named Nola attacked them making them split. After finding himself all alone, Chopper was caught in the cross fire between Enel's enforcers and Shandians. Chopper eventually found himself on the Ordeal of Swamp where Gedatsu, one of the priests awaits there. He mustered up his strength and defeated Gedatsu. Confident on being on his own, Chopper proceeded to the Upper Yard, but he encounters Ohm, who defeated him. He regained consciousness when Luffy finally rang the bell.

Later he was seen joining in the celebration. The next day, the crew has collected a large amount of gold when a group of Skypieans arrive with Robin bringing a large gold post, but the rest of the Straw Hats mistake it for a large cannon and they start running to their ship. They manage to return to the Blue Sea with the help of Pagaya and Conis.

The Davy Back Fight
Chopper and company come across a mysterious pirate ship after trying to escape a giant wave. Soon, they arrive on an island inhabited by strange animals. Going Merry is captured by the Foxy Pirates. After Tonjit re-unites with his horse, they are soon attacked by Captain Foxy and his subordinates, who challenge Luffy in a Davy Back Fight, a contest of pirates where the stakes are members of the crew.

The first round of Davy Back Fight involves a race around the island with tiny boats. In the anime, Chopper is teamed up with Zoro, and their boat has been eliminated immediately. With only Luffy, Nami, and Porche's boat remaining, it's an all out war to the goal, but after Foxy exposes his Devil Fruit powers, Porche wins and takes Tony Tony Chopper from Luffy.

When Foxy decides to take Chopper after the first round, the "Donut Race," Chopper cries, saying that he only went out to sea because he knew that his nakama will be the Straw Hats. Zoro lectures Chopper, telling him that he must be a man and that he is responsible for becoming a pirate.

The second round prepares to start. Without Chopper, Sanji and Zoro must face the Foxy Pirates in a ball game, but are hampered by their blatant cheating and the crooked referee. The bickering rivals Sanji and Zoro manage to overcome the opposing team by working together. Luffy takes Chopper back. (In the anime, Luffy chose Shelly instead of Chopper.)

Luffy and Foxy face off in the final game: a battle of brawn aboard Foxy's ship. The Straw Hat pirates watch from the side as Luffy continues to battle Foxy with the odds not in his favor, and the fight continues inside Foxy's ship. They have not seen the battle when they fight inside the ship. Luffy manages to finally defeat Foxy by using his ability against him. After Foxy's defeat, the Straw Hats leave in search for a shipwright.

Water 7: A Breaking Ship, a Breaking Crew
After the Going Merry narrowly escapes being hit by a "sea train," the crew meets an old woman, Kokoro, and her granddaughter, Chimney. Kokoro gives Luffy a map to Water 7. Chopper loses Robin when she was gone shopping.

Chopper, along Luffy, Sanji and Zoro follows Usopp's bloody trail to the Franky House where they find him passed out in front. The four of them challenge the Franky Family only to find out that their real target, Franky himself, is gone and has taken the money with him.

After talks between Luffy and Usopp break down into a fight, ending with Usopp being greatly wounded by Luffy, Chopper attempts to go to his aid. Sanji attempts to stop him, though, saying that Usopp asked for the duel, and getting healed by Chopper would only bring him shame. Despite Sanji's request, Chopper went to Usopp, leaving behind medical supplies as he tearfully ran back to ship.

The Straw Hats get themselves a hotel room. An incredibly high tide called the "Aqua Laguna" is coming and Chopper and Sanji rush to warn Usopp. While the crew hide from angry residents, Sanji and Chopper discover Robin and she tells them what they've feared: she's responsible and she wants to part ways. Chopper reunites with the others without Sanji and they discuss what's happened. Luffy decides that in order to know the full truth, they must catch Robin.

The Straw Hat Pirates and Paulie break into the room where they find Iceburg and CP9. Luffy and the others request that Robin comes back to the crew. She refuses and tells them that she cannot accomplish her "wish" if she were to stay with them. Robin turns to leave and CP9 try to hold the pirates back. Robin successfully escapes and Lucci shows those remaining his "transformation." Lucci's transformation is a result of a Devil's Fruit; a Zoan Type leopard. He quickly disposes of the crew and CP9 tie up Paulie and Iceburg, leaving them alone as the building slowly burns down around them. Chopper escapes the burning building with Paulie and Iceburg on his back and collapses outside. Nami rushes to tell Chopper so they can go looking for the rest of the crew.

Chopper finds Zoro and hands him the Sandai Kitetsu so he can escape the chimney. Seeing how determined Luffy is to save Robin, Kokoro and Iceburg lends the Straw Hat crew the use of another sea train, Rocket Man. The Franky Family shows up, pleading with Luffy to let them join them because they'll do anything for their leader. The Rocket Man finally makes it out to sea.Paulie tells his fellow carpenters who the real culprits were. The Straw Hats, Franky Family, and Galley-La Company form an alliance.

They miraculously pass through unscathed Aqua Laguna and the passengers rejoice. Sanji contacts the rest of the crew and fills them in on his current situation. Back in the Rocket Man, Luffy, Zoro, Nami, and Chopper get an outfit change. Those on the Rocket Man encounter the discarded cars and Zoro slices them so they can pass. Zoro clashes with "Ship Cutter" T-Bone. The fight is short and Zoro joins the crew again in the Rocket Man.

Yokozuna the frog jumps onto the front of the train, knocking them from the rails. After Kokoro speaks with him, he joins the group. Luffy and the others finally catch up to Sanji, Usopp, and the rest of the Franky Family as they near Enies Lobby. Paulie sits down with the group and talks about their plan. Luffy does not bother to follow the plan, and slingshots himself beyond the gates before the train stops.

Rescuing a Nakama from Enies Lobby
As they proceed to Enies Lobby, Chopper and crew manage to land on Oimo's back. They ride Sodom and Gommorah to reach the Courthouse. As they wait for the bridge to be activated, they lined up at the roof to convince Robin to accept their request saving her. When the bridge was not fully lowered, Kokoro helped by using the Rocketman. The train used the half lowered bridge as a ramp. Luffy pushed them all down as he jumped onto it.

After they crash-landed, Fukuro appears and declare that a key is needed to uncuff Robin's cuff. The crew decided to individually search for and fight an agent, leaving Luffy to handle Lucci whom Fukuro said was taking Robin to the Gates of Justice. Later, searching for agent, he found Zoro and Sogeking being chased by Kaku and Jabra cuffed each other. He was sent to search for the number 2 key from the other agents.

He switched with Nami to fight Kumadori. As the second Rumble Ball does not work properly, he was beaten well. Desperate, he defeated Kumadori by eating a third one, losing his rationality and conscience in the process. He was shot by Franky's "Coup de Vent" which sent Chopper soaring sea in order to stop Chopper's violent rampaging.

He has been carried by Kokoro after he got saved by Franky. When he woke up, he and his crew mates had been saved by Kokoro from drowning, who is a mermaid. As his crew mates defended the escape ship, he could not move his body because of the side effect of the overuse of the rumble ball.

With the help of the Going Merry, everyone managed to escape Enies Lobby safely (while painfully pulling Zoro's legs to get him to apologize to Robin). However, after escaping, Iceburg arrives in a Galley-La just in time to pick up the Straw Hat Pirates as the Merry suddenly breaks apart. Luffy then gives the Going Merry a viking funeral by burning the ship as the crew tearfully says goodbye.

Chopper received his first bounty of 50, so low because he was perceived to be the "pet" of the Straw Hats. This possibly gives him the smallest active bounty of all time. Chopper is shocked and disappointed that his bounty is so small, since he believed he fought like a man.

When Monkey D. Garp attacks and Usopp tries to rejoin, Chopper was the only one who did not deny his attention.

Adventure on Ghost Island
After sailing for some time on the Thousand Sunny, Chopper and the rest of the crew came across a mysterious barrel floating on the ocean. Upon opening it, a flash shot up from it. After braving a storm that mysteriously came afterwards thanks to Nami and Franky,Chopper and the rest of the crew found themselves in the presence of a ghost ship.

This ship apparently belonged to a skeleton named Brook who through by chance initially accepted Luffy's offer to join the crew. Chopper along with Usopp were exceptionally afraid of the skeleton. Just as Brook was about to perform before Usopp and the rest of the crew after dinner, a ghost appeared, and a clanking noise was heard. These sounds were caused by the gates of the island that suddenly appeared, Thriller Bark, closing. This prompted Brook to head to the island before Chopper and the rest of the Straw Hats' eyes.

With Luffy's resolve to go to the island, Chopper could not do anything about it. With Usopp and Nami, he set out in the new 'mini-merry' ship to explore Thriller Bark. There, the three met the Cerberus, which chased them until they hid in a tree. Here the three met Hildon who decided to take them to met Dr. Hogback. This pleased Chopper as the doctor was renowned in the medical world.

After riding a carriage with Hildon through some woods filled with all sorts of stitched-up creatures, Chopper and his companions were left in the middle of a cemetery. There, they were attacked by some Zombies,and escaped into Hogback's mansion and met with the good doctor and his maid, Victoria Cindry. Over dinner, Chopper asked for the doctor's autograph and a chance to visit his laboratory. The former request was given to Chopper but the latter was not.

After dinner with the good doctor in which the three asked about Brook, Nami decided to take a bath. For this, Chopper and Usopp were put in charge of guarding her from intruders from the outside. In the middle of the bath however, Nami was attacked by an invisible thing. Luckily, Usopp came in the bathroom and drove it away. Later after the incident in the bathroom, Chopper and his companions found out that the paintings and taxidermy in the dining room were all Zombies. Fortunately, the three escaped through a secret door before the Zombies could catch them.

Beyond the secret door, Chopper and his companions found themselves in a room filled with Cindry's pictures. Through a newspaper article that Nami found, the three learned that Cindry was an actress that died ten years ago. Just as they were about to leave, the three stumbled across a treasure chest. Inside however, was a horrific Jack in a box that frightened the three out of the room.

As the three were running through the hallways of the mansion from more painting Zombies, a mysterious bodyguard decided to chase them.

Eventually, Chopper along with Usopp and Nami hide inside the stuffed body of Kumashi to overhear Moriah's plan for creating Oars- the strongest zombie. Eventually the trio are discovered and make a run for it, but are surrounded and attacked by a large group of Zombies. During the battle, Nami is captured by Absalom. Franky and Robin arrive just in time to finish off the zombies. After that the crew makes its way back to the Thousand Sunny where they find Luffy, Zoro and Sanji. After explaining the situation to them, Luffy orders the Straw Hats to prepare for a counterattack on Thriller Bark.

With Robin, Chopper attacked Hogback in his laboratory, but found him protected by Jigoro, Inuppe, and Cindry. Chopper and Robin fight them, but are eventually forced into submission. Chopper announces his disgust and defiance by declaring Hogback is no longer a doctor to him. He explains that when Hogback told him he was using the zombies to investigate the difference between life and death, he admired him because he could help those who lost loved ones when death occurred, but when he found out his role in the zombies' resurrection, he was disgusted that he would go as far as to use them for personal benefit instead medical science, and is forcefully moving them despite their hearts not beating, making them puppets. This, Chopper explained is why he cannot accept the zombies as living creatures, and Hogback as a doctor.

Hogback laughed and insulted Chopper's ideals, declaring he brought new life to the zombies and they should be grateful for "reviving" them. He demonstrated their proof of being "alive" by kicking Victoria Cindry in the face and ordering her to lick the ground. He explained that the room that Chopper went into earlier was his room, and told him how he disappeared, and the truth behind Victoria Cindry and her death.

He explained that because of his medical genius, many flocked to him with the hopes he could help them or their loved ones. Eventually, he could not be bothered with, and explained it was only for the money. Then, a beautiful and famous entertainer named Victoria Cindry became one of Hogback's patients. Hogback, like many other men, was smitten by her beauty and fell in love with her, but she told him she was already engaged. However, it was nothing compared to his eventual heartbreak when he found out Cindry lost her life when she fell from a stage. A depressed Hogback left his job and disappeared from public knowledge, but was discovered by Gekko Moriah and became in his servitude in the promise that Cindry be brought to life.

Eventually, he stole Cindry's corpse and with medical surgery and Geko Moriah's Kage Kage no Mi ability, Cindry was brought back to life as a Zombie. Hogback declared although Cindry had a different personality, he cared only for her beauty and said she is and should be thankful for her resurrection, and thus ordered her to attack Chopper.

While Chopper refused to attack her, and merely restraining her, as she continued to assault him. Chopper pleaded to Cindry to stop and look at what she's become. While she calms down, Chopper asks to Robin to use her powers and feed her salt. However, she was prevented from doing so by Jigoro and Inuppe under Hogback's orders. Later, it soon became apparent that the two zombies could not get along and began to fight each other, just like Zoro and Sanji so Robin took advantage of Hogback's orders by forcefully closing his mouth, asking him to order herself and Chopper to "jump off the tower." When Robin released Hogback, he indeed did give this order, but it was mistakenly given to Jigoro and Inuppe and they followed suit.

Chopper decided to pummel Hogback, as the mad scientist desperately gave orders to Cindry to buy her time, but she miraculously started crying, and said she could not move. Just as the battle is turning in the Straw Hats' favor, with Chopper with Robin's help about to deliver the final move on Hogback, Oars however, demolished the wall and interrupts the fight. As Hogback pleads for Cindry's help, she simply smiles, implying her soul temporarily returned to her, and leaves him and herself to their fate. Oars' rampage apparently leads him to crush both Hogback and Cindry.

Chopper joined the crew's battle against Oars, and although the battle was completely drastic, it became increasingly desperate when Gekko Moriah used his Kage Kage no Mi ability to manipulate Oars' body, giving him an ability to stretch like his counterpart, Luffy. Despite to Oars' immunity to pain, Chopper discover that his weak spot is his right arm. It was discovered that Oars suffered a severe case of frostbite, due to wandering the Frozen Continent with very little on.

Chopper, Sanji and Zoro made continued attacks towards Oars' right arm, taking advantage of Oars' inability to feel pain, and giving his right arm considerable damage (though not initially noticed by Oars), however Chopper along with Sanji was knocked out for these efforts. With the Straw Hats falling one by one, Luffy returns to save Nami and Usopp and with 100 shadows in him, Luffy strength multiplied several times over becoming "Nightmare Luffy" and proceeded to pummeling the zombie giant, beating him severely, with Moriah himself caught in the attack, before powering down.

Down, but far from out, Oars gets up to do battle again. Fortunately, Nightmare Luffy's attack was more than enough time for the Straw Hats to recover. Luffy himself surprisingly gets up despite having the exhausting process of 100 shadows in his body for ten minutes. Chopper concocts a plan to force Oars' back straightened to take the full force of Luffy's attack. With his arm broken, Oars cannot counter as Luffy activates Gear Third smashing a Gomu Gomu no Gigant Bazooka to his face, breaking Oars' back.

However, Moriah returns to consciousness, and uses his ultimate technique Shadows Asgard, taking all shadows in Thriller Bark, numbering to 1000 to finish off the Straw Hats once and for all. However, as Chopper witnessed, Luffy activated both Gear Second and Gear Third at the same time, and finally defeated Gekko Moriah, releasing all the shadows. Nami then remembers Kuma is on this island and tells everyone.

Meanwhile, Kuma reports that Moriah has failed to kill Luffy and is badly wounded, he is ordered to kill everyone on Thriller Bark and evacuate the wounded Moriah. However, instead of outright killing everyone as his orders said he offers everyone a deal- let him kill Luffy (who cannot fight back now) and he will leave everyone alone. The Straw Hats and everyone else on the island tell Kuma no way and he sets off a bomb made out of air that knocks everybody unconscious.

However, before he can finish off Luffy, Zoro rises again and vows he will not let Kuma touch him, Kuma offers to just kill Zoro then and attacks him, though Zoro survives. Zoro offers his head for Luffy's and Kuma decides to torture Zoro by giving Zoro all the pain and suffering Luffy had endured. Kuma then leaves, praising Luffy for having such good friends.

Soon after, Chopper joins everyone in a celebratory party at Thriller Bark (save for Zoro, who is still recovering from his wounds) lead by Brook and his piano. Luffy finally reveals to Brook that he is friends with his nakama, Laboon. Brook stops partying, cries, and reveals a Tone Dial which has the last song the Rumba Pirates ever performed together on it. Brook states that since he has new friends in Luffy and the others, he no longer needs the Dial and will give it to Laboon the next time they meet. Brook then asks if the Straw Hat crew invite is still good and Luffy says it is, Chopper joins the others in a shocked response.

Once he and the rest of the crew finally left Thriller Bark, they held a toast to Brook, their new nakama.

An Incident with the World Nobles
After leaving Thriller Bark, Chopper assisted the other Straw Hats on their continued journey. He helped fight the Flying Fish Riders alongside the crew.

Afterwards, he arrived in the Sabaody Archipelago, where he joined in the initial group heading out on the island. He was treated to cotton candy by barmaid Shakuyaku and eventually dozed off alongside Brook after trying and failing to find the assisting Keimi. Usopp later found him and Brook and was berated for relaxing instead of looking for Keimi, and they were quickly taken aboard a Flying Fish with the Rosy Life Riders.

After they enter there, Keimi had already been sold to Tenryubito Saint Charloss in an extravagant bid of 500,000,000. However, Luffy's Flying Fish burst in, and he quickly got off to rescue Keimi. In former enemy Hatchan's attempt to restrain him, he inadvertently revealed he is a fishman and is shot by Carlos Sei. An enraged Luffy responded by punching him in the face, and starting an incident attracting several Marines to the Human Auctioning House. Luffy, along with the crews of two of the Eleven Supernovas, Eustass Kid and Trafalgar Law cleared the incoming masses of Marines, Chopper assisted them in battle, until he as well as the rest of the Straw Hats with the help of Duval's Rosy Life Riders, managed to escape.

Destruction of the Straw Hat Crew
Chopper heard Rayleigh's story with the others, but shortly after leaving, he and the others were confronted by a Pacifista. Chopper's Roseo Meitel attack did very little damage to the weapon's defenses, but the group managed to defeat it by combining their efforts. Unfortunately, they were soon confronted by a second Pacifista and Sentomaru, Dr. Vegapunk's bodyguard. Luffy ordered the crew to split up, and Chopper went with Luffy and Robin. Sentomaru intercepted Luffy and managed to wound him with unarmed attacks despite his rubber body.

Seeing his companions defeated, Chopper became desperate and used three Rumble Balls at once, although he had already used one against the marines outside the Human Auctioning House and another against the Pacifista, it transformed him into Monster Chopper. Monster Chopper then began attacking Sentomaru as Robin fled with Luffy. He turns his attention to Kuma who just appears and is vanished as a result.

Straw Hat Separation Adventure: Torino Kingdom
Chopper lands in the Torino Kingdom, in the South Blue, where the natives want to cook him. As seen in the Straw Hat separation serial, Chopper is running for his life to avoid getting eaten. At some point, he managed to hide while the natives were fighting the giant birds on the island.

After some time on the island, Chopper manages to stop the war between the humans and birds, using his ability to talk to animals to translate for the natives. Afterwards, he leaves the island worried and wanting to heal Luffy's wounds after learning of his involvement in the war and Ace's death. He flies off the island on one of the birds, though at the same time a News Ku passes by, and after reading the paper Chopper is shocked by a recent article involving Luffy.

He states he understands why Luffy is praying at Marineford, and afterwards, he returns to the Torino Kingdom to become stronger. Since Chopper is uncomfortable with returning to the island sooner than expected, he wears a disguise called "Chopper Mask". However, the natives instantly recognize Chopper and the reindeer then threw away the disguise.

Chopper says that he wants to study the plants on the island and a native takes him to the village library where he can do his research. Chopper then comments that the natives are not as primitive as he originally thought as he recalls them using mechanical weapons. Chopper then thinks back to his early days, where he was called a monster and shunned by everyone. He realizes that ever since he joined Luffy's crew, it did not matter what other people called him, and he promised to help Luffy no matter what.

The Straw Hat Reunion
After two years, Chopper returned to Sabaody Archipelago. Chopper is seen following Fake Zoro, Fake Sanji, Fake Robin, and his own counterpart, believing them (excluding Fake Chopper) to be the real ones. After Fake Robin tries to lure Chopper to them with a cucumber, Chopper then witnesses the fake Robin getting kidnapped by some mysterious men. Later when he sees the Impostor Straw Hat Pirates, he is disappointed in his "captain" and that they are not going to save "Robin", and he leaves crying and saying that he will save her himself.

While searching for "Robin", Chopper ran into Usopp and Nami, who are very happy to see him. After Chopper is informed that the Straw Hats he encountered are fakes, he returns to the Thousand Sunny with Usopp and Nami. Franky then amazes Chopper and Usopp with his new upgrades. Chopper gets excited wondering what Franky's new weapons are. He was pleasantly surprised when he heard from Rayleigh that Luffy was already in the archipelago.

After arriving at Grove #42, Chopper departed atop one of his enormous bird friends from Torino Kingdom to bring Luffy, Zoro, and Sanji back to the Thousand Sunny. With the assistance of the Straw Hats' new allies, Chopper and the rest of the crew descended into the ocean with their coated ship, finally resuming their adventure after two years.

Undersea Voyage
While sailing under the ocean, Chopper and the crew marvel at the site of the underwater world. He and Usopp also had to keep Luffy and Zoro from doing anything that might endanger the crew. He attends to Sanji after the cook recieved a massive nosebleed. Chopper along with the rest of the crew decides to have lunch, while Franky explains how their ship was in one piece after two years. As the ship descends even deeper, the crew marvels at how dark it has become. With their seacow, the Caribou Pirates soon caught up with the Straw Hats and prepare for battle. Caribou jumps onto the Thousand Sunny. Before his crew can follow, his seacow, which turns out to be Mohmoo fled in fear after seeing Nami, Sanji and Luffy, leaving Caribou behind. The Straw Hats then tie up Caribou as he begs for mercy. Caribou claims that he is an unfortunate victim and not a pirate and Chopper believes him until Usopp points out that he is lying.

Chopper then attends to Sanji as he experiences another massive nosebleed, suggesting that they try to rehabilitate Sanji. He listens as Nami, with the help of Brook, Franky and Robin explain about the Sea Currents, but quickly loses interest when Nami starts talking about how salinity affects them.

He reacts with shock when he sees the Kraken. He then screams in terror when he witnesses the Kraken destroying Caribou's ship. Even though the Monster Trio leaves the ship using Barefoot Coating to fight the Kraken, the sea monster aims for the Thousand Sunny. Franky uses his rocket launcher to repel one of the tentacles which amazes Chopper.

Chopper then blocks another tentacle with his new Guard Point. The Monster Trio soon defeats the Kraken, but because they are not wearing life-lines, they got separated from Chopper and the rest of the Straw Hats as the ship goes down the underwater current.

When the crew reaches "The Underworld of the Sea", Chopper immediately starts to look for the missing Monster Trio along with Usopp and Brook. He then notices the gargantuan size of a school of jellyfish that are floating around the ship. One of the jellyfish puts one of its tentacles through the bubble coating. Chopper reaches out to touch it but Robin stops him, saying it is probably poisonous, much to Chopper's stunned surprise. When an even larger fish ate the jellyfish he almost touched, it died as a result, confirming to Chopper that Robin's theory about the jellyfish probably being poisonous was correct. The reindeer commented on how scary and dark the Deep Sea is and how the fish in it cannot see too well.

When the crew realized Caribou was gone, Chopper thought one explanation was that he was thrown overboard while going through the downward current. Chopper was scared when Nami suggested that Caribou might still be hiding on the ship. After Franky trapped Caribou in the barrel, Chopper is the first to notice a sudden rise in temperature. He then moans about how hot it is, saying he cannot go on living like this way, and how after waiting two years to see Luffy, Zoro, and Sanji, they disappear. When the ship is about to be eaten by a gigantic angler fish, Chopper foams at the mouth in shock.

When the under-sea giant, Wadatsumi appears, Chopper starts to cry from sheer terror. He screams in fear when the Flying Dutchman appears. He, along with Usopp, is shocked by Brook's frightened reaction to the ghost ship. He is shocked to see Surume suddenly show up and knock out Wadatsumi, and overjoyed with the rest of the crew to that the Monster Trio is back safely. When they are on board, Chopper tackles Luffy, telling him how scared he was.

When the underwater volcano starts to erupt, Chopper panics and is thrown back by the rest of the crew. Chopper exclaims how hot it is when Nami says the water temperature is rising. When Sanji suffers a nosebleed while talking to Nami, Chopper remarks that it is a bad time to have a guilty conscience. When the crew reaches the trench, Chopper notices how the water is making steam from the heat. When the rocks fall into the trench, he marvels at Usopps new attack. When a stray rock hits Surume, Chopper falls with the rest of the crew to the bottom of the sea.

Upon reaching Fishman Island, Sanji suffers another nosebleed thinking about mermaids. Chopper tells him that it would be best if he did not see any actual mermaids, as doing so could kill him. He is impressed with Sanji's fiery resolve to die while seeing mermaids. When Hammond approaches with his group of sea monsters, Chopper is shocked by their gargantuan size. Hammond gives the crew two options: join the New Fishman Pirates or die. Chopper and the rest of the crew then prepare to enter Fishman Island with a Coup de Burst.

Trouble in the Underwater Paradise
Luffy rejects Hammond's offer of joining the New Fishman Pirates and the fishman prepares to attack. Franky activates Coup de Burst and the ship flies through the bubble surrounding Fishman Island. The ship then falls into a current and the crew got separated. Chopper, Luffy, Sanji, and Usopp are seen again in Keimi's house meeting and getting reacquainted with Keimi. Keimi introduces them to some of her friends, the Medaka Mermaid Quintuplets and takes them to Mermaid Cove where they meet more mermaids.

As Sanji swims with the mermaids, Luffy, Usopp, and Chopper relax. Chopper expresses his surprise that Sanji is back to his normal self, wondering if it was in the chef's nature. He also says that he is glad that Sanji is feeling better, as he had run out of Sanji's blood type in his blood stock. Chopper states that Sanji has a rare blood-type and that he will not be able to treat any more nosebleeds. While Keimi is telling Luffy that Jinbe is not present on Fishman Island, Chopper is seen in the background looking shocked at a sea serpent that has just appeared behind Usopp. When the killifish mermaid quintuplets inform them that a royal gondola is approaching, Chopper, Luffy, and Usopp hide behind cover while Sanji is being covered by a mermaid. The three brothers of the Neptune House appear, searching for the people who entered Fishman Island illegally. The mermaids deny that they have seen any intruders.

As the three brothers are leaving, Sanji suffers his worst nosebleed to date, forcing the Straw Hats to reveal themselves. As the Ammo Knights start advancing, Chopper pleads for them to stop and help Sanji, asking if anyone could donate blood. He explains that if they do not get blood for Sanji, he will die in half an hour. Chopper asks if there is anyone who has a blood type of S RH-, going on to say that it is extremely rare. Keimi tells Chopper that fishmen and merfolk have the same blood as humans and it is transferable. She is about to explain further, but Hammond interrupts her, continuing her explanation. He explains that there has been a rule in place for a long time stating it is forbidden for humans and fishmen to share blood. He goes on to say how Fisher Tiger supposedly died. After a gruesome battle, Fisher Tiger suffered a critical blood lost and could have been saved with a blood transfusion, but humans refused to help him. Hammond adds that the rule was put in place by humans ages ago so that their bloodline would not mix with "monsters".

Hammond and his group attempt to capture the four Straw Hats, but Luffy repels them. When a sea monster in the New Fishman Pirates tries to attack Luffy, the Straw Hat captain subdues it with Haki. Chopper and Usopp are shocked by how the monster acknowledged its loss without actually fighting. Keimi steals the royal gondola and helps the four Straw Hats escape. After Usopp notices Sanji's smirk and Chopper yells at Sanji to not think about anything as every second matters, Keimi then takes the group to the town port.

At the town port, Keimi and the four pirates find shelter in Madam Shyarly's Mermaid Cafe. Madam Shyarly provides them a room where they can treat Sanji. Chopper and the others luckily come across Splash and Splatter, a pair of okamas who happily agree to donate blood to Sanji. After Sanji receives a blood transfusion, Chopper is relieved that Sanji is able to wake up. Chopper also notices that Luffy got a scar on his arm when he attacked Hammond and his two companions. Chopper checks Luffy's blood and see that Luffy got poisoned by the octopus merman and is amazed that Luffy's body is able to fight against it. Chopper stays with Sanji to ensure his recovery.

When the Ammo Knights try to arrest him and Sanji because of Madam Shyarly's premonition and because of the false accusation for mermaid kidnappings, along with the fact that the majority of the other Straw Hats were holding the staff of Ryugu Palace hostage, Chopper uses his new Kung Fu point to fight them off, something that the soldiers and citizens thought was a weird animal. Having slightly recovered, Sanji tells Chopper that he is going to see the Mermaid Princess, even if he dies. Chopper scolds him, telling him that if she was beautiful, Sanji might die instantly.

Sanji then defeats the rest of the Ammo Knights and expresses his disappointment of having to give up his chance of going to Ryugu Palace since they were trying to handcuff him. Chopper scolds Sanji for overdoing things, but Sanji snaps back saying whats done. Sanji then compliments him on his Kung-Fu Point and the reindeer happily dances while claiming to be not happy. When they hear people screaming that a bloodied person is found and needs a doctor, Chopper turns to their direction and says that he is a doctor. Chopper and Sanji then find a wounded Hatchan, who warns them of an impending attack by the New Fishmen Pirates.

Chopper then tends to Hatchan's wounds while the doctor and Sanji are met with accusations from the Fishman Island citizens. While hovering above Coral Hill on top of Megalo, Luffy sees them and jumps down to meet them. Megalo, who is holding Princess Shirahoshi in his mouth, reaches his limit and spits her out. While the Fishman Island citizens instantly conclude this as a Mermaid Princess kidnapping, Chopper yells at Sanji to not turn around or else he might die from another nosebleed.

For the sake of his dream, Sanji decides to turn around even if it means death much to Chopper's horror. However, instead of getting a nosebleed, Sanji becomes petrified. Chopper says that it must be the effects of the Okama blood transfer. The citizens then tie up Chopper and the group, but are interrupted by the arrival of Vander Decken IX. After Luffy pummels Decken into the ground, he checks on Sanji. Chopper informs him that Sanji has reverted to his normal state. The princess and the entire group then hop on Megalo and fly away. After Luffy beats back Wadatsumi, the entire group head for the Sea Forest.

After reaching the Sea Forest, Chopper decides it is safe for him to take his time to treat Hatchan's wounds. The group then get acquainted with Franky, Den, and Jinbe. Chopper then tells Franky that he is going to lower Hatchan down from Megalo, and he should be ready to grab him. After Hatchan is lowered, Chopper is surprised to see that Sanji is acting like his old usual self in front of Shirahoshi. Nami and Keimi soon arrive and Chopper happily realizes that Sanji is finally cured of his nosebleed tendencies. While Chopper makes medicine, he listens to Jinbe as he explains the dark past of the fishmen and merfolk as well as the ideals of Queen Otohime and Fisher Tiger.

After Jinbe finishes his story, Chopper and Nami have a friendly conversation with Princess Shirahoshi. When Hatchan starts explaining Hody's plan, a visual Den Den Mushi appears and the group watches a visual broadcast by Hody Jones himself.

Hody explains his plan of recreating the Ryugu Kingdom with himself as the ruler and then addresses the Straw Hat Pirates. Once he shows the imprisoned Zoro, Usopp, and Brook, Chopper is shocked. After Hody finishes his speech, Luffy resolves to fight him. However, Jinbe tells him not to. Chopper and Franky then correctly guessed that it's because they are humans. Chopper then watches Luffy and Jinbe try to settle their dispute on how to deal with Hody.

Battle for Fishman Island
Chopper later appears in Gyoncorde Plaza with the rest of the Straw Hats preparing to fight against the New Fishman Pirates. When Franky mentions a new weapon in the Soldier Dock, Chopper gets on board it along with Usopp, Nami, and Pappug. He keeps asking Usopp if he can drive it. He then rides out on the Brachio Tank V, calling himself "Commander Chopper."

When the Brachio Tank IV falls in a pitfall created by Daruma, Chopper is thrown out with the others by Franky. He then goes underground, using his new Horn Point and hinders Daruma in making more pitfalls. He launches him back to the surface and when arrived there, Luffy mistakes his new form for a stag beetle. Chopper then faces off against Daruma.

Chopper is underground with Daruma when Usopp calls out for him. Dosun gets behind Usopp and tries to take him by surprise, but Chopper intervenes using Horn Canon: Elf to push Dosun back. While Usopp prepares to fight Daruma, Chopper prepares to fight Dosun.

Later, Chopper comments on the new attack from Iron Pirate Franky Shogun, but is shocked to see that Franky was the attacker instead of the machine. Dosun tries to take advantage of this, but Chopper transforms into his new Heavy Point and matches Dosun's T-Shot with a Heavy Gong. As he recoils from the force of the attack, Zoro comments on the new monster appearance of the transformation, which Chopper willingly accepts.

Later, Chopper is seen rampaging in his 'Monster Point' much to Usopp's surprise. Usopp nervously tells Chopper that the situation is not that serious for him to go like that. Then, Chopper turns to him and says that he is alright, meaning that Chopper is in fact still conscious.

After explaining to Usopp that he can use one rumble ball to stay in Monster form for three minutes, he turns back to Dosun and easily knocks out the fishman with his Kokutei Parmei attack. After all the leaders of the New Fishman Pirates have been defeated, the Straw Hats look into the sky as Luffy tries to destroy Noah. When the Sea Kings appear and stop Noah from falling, saving the ship and the island at the same time, everyone on Fishman Island celebrates.

The After Battle Celebration and Departure
Moments later Shirahoshi brings Luffy to the plaza, dismayed to inform everyone that Luffy lost a lot of blood. Chopper then asks the citizens if any of them has type F blood. He then recalls of the law prohibiting fishman-human blood transfusions. When Jinbe steps up and volunteers to donate blood, Chopper carries out the procedure.

Luffy invites Jinbe to join the crew, but Jinbe declines, saying that he has some unfinished business. Chopper and the rest of the crew inform Jinbe he is welcome to join whenever he is ready.

Neptune invites the crew to a banquet and the crew party at Ryugu Palace with the royal family. After partying for a while, Chopper is shown enjoying himself, when Jinbe recounts the conflict between Aokiji and Akainu. Chopper proudly states he has already heard about it. He then expresses dismay that the Blackbeard Pirates are hunting strong Devil Fruit users. He believes that he would be a target, but Usopp points out that they would not need the Hito Hito no Mi. After the party ends, Chopper is talking with Usopp about the treasure Luffy, Zoro, and Sanji went to collect. He suggests they help them search and is surprised about how high Caribou's bounty is. Chopper and the rest of the crew are later shocked that Luffy challenged Big Mom.

Afterwards, Chopper and the rest of the crew bid the citizens of Fishman Island farewell and promise (except Franky and Zoro) Shirahoshi to take her to the surface someday. The crew set sail with the Thousand Sunny and head towards the New World.

On their way to New World, Nami puts Chopper to guard while she takes shower using her Shower Tempo. Chopper remarks how the Shower Tempo clouds look sweet and yummy like cotton candy and shows his concern if the crew will be alright with Nami not on the deck. After the crew reaches the New World, Chopper comments on how the sea of New World looks red.

Arrival at Punk Hazard
Soon after entering the New World, the crew spots an island surrounded by a sea of flames. The Straw Hats then receive a distress call from someone who seems to be in trouble and mentions something about a samurai. After Luffy decides to go rescue the person, Chopper expresses relief that he was not one of those chosen to accompany Luffy on his exploration mission, stating that he is not good with heat.

While Usopp, Robin, Luffy, and Zoro fight a dragon, Chopper and other Straw Hats remaining on the Thousand Sunny are knocked out by sleeping gas. They, except for Brook, are then abducted by some unknown foes. The captured Straw Hats later wake up in a cell and find parts of a samurai's still-living head. After putting the pieces of the head back together, the group gets information from the samurai. Once they decide to break out, Franky uses his Radical Beam to blast a hole in the wall, allowing the crew to escape. They run down through the halls of the complex and stumble upon a room filled with giant children. The children are excited to see them, but Sanji just wants to escape the room before they are recaptured.

While their pursuers come after them, the children begs the pirates to help them escape. Nami could not ignore their cries and decides to help them. Sanji, Franky, and Chopper then attack the men in the gas masks. Nami and Chopper run away with the children while Sanji and Franky hold the enemy back. Since he was entrusted with protecting the children, Chopper is determined to live up to Sanji and Franky's expectations. As they run, the children tell Nami and Chopper about how they were abducted and that they were inflicted with some kind of disease. Nami is suspicious, and tells Chopper to later investigate the children. They then run into a room with corpses frozen in the walls, floor, and ceiling.

Frightened, the group escapes and meets up with Franky, Sanji, and the head of the samurai, and they all run out of the building and into the shocked view of the Marines of G-5, Smoker, Tashigi, and Law. They immediately turn around and try to find another exit to avoid any combat. As they are running away, Law uses his ability to rearrange the personalities of the Straw Hat Pirates, putting Chopper in Sanji's body and Franky in Chopper's body. After escaping, Chopper (in Sanji's body) helps keep Nami (in Franky's body) from hurting Sanji anymore than she can. The group then reunites with Zoro, Luffy, Robin, Brook, and Usopp at the back side of the Punk Hazard facility. The Straw Hats then tie up Brownbeard and bring each other up to speed on the current situation. After interrogating Brownbeard, they learn about a man known as Caesar Clown.

Kinemon later leaves the group to find his torso and Sanji, Brook, and Zoro go out to find him. In the meantime, Chopper begins to examine the children and the source of their sicknesses, while Franky (in Chopper's body) experiments Choppers abilities and makes weird faces. Before long, several of the giant children start to feel pain, saying that they need candy usually given to them in order to make the pain go away. However, Chopper states that the candy contains a drug that the children became addicted to and Luffy's group learns that the children have been experimented on. One of the giant children hits Luffy and the others go on a rampage, forcing Usopp to put them to sleep. Chopper expresses his sympathy towards the children and Luffy's group decide to help the children and find Caesar. The group then tie up the giant children so that they cannot destroy anything else. Luffy, Usopp, Franky, and Robin then leave Chopper and Nami to watch the children while they head to Caesar's lab. While they are gone, the Yeti Cool Brothers attack and gun down Brownbeard. By the time Luffy's group returns, they kidnap Nami.

Luffy and Franky decide to go after the brothers. Franky asks Chopper to give him some Rumble Balls. Chopper gives him one and advises him on how to use it. However, Franky immediately takes one, transforms into Monster Point, and goes on a rampage while chasing after Luffy.

Alliance with Law and a Plan to Defeat Caesar Clown
After the defeat of the Yeti Cool Brothers, Luffy, Franky, Nami, and Law return to the hideout. Chopper and the rest are shocked that Luffy formed an alliance with Law. Law then returns Chopper to his body and Franky to his. Chopper then scolds Luffy and Franky for causing damage to his body. When the Straw Hats insist Law to assist them in helping the children, Law asks to take Chopper with him to help find the medicine that was used on the children. Usopp ties Chopper to Law's hat, while the rest laugh at Law. Chopper is then tied to his nodachi instead.

Law later warps both himself and Chopper to the back side of the facility to begin their part of the plan. The two briefly discuss on how they are going to investigate the drugs. They are later seen inside, where Law manages to lead Monet away while Chopper (hiding inside Law's bag) is left in the room unnoticed. Chopper then leaves his hiding spot and starts sneaking around in the facility.

He later finds Luffy's group in Caesar's clutches. Before Caesar sends them outside to die by the poisonous gas cloud created by Smiley, a piece of paper is hurled at Chopper. Chopper then reads a note, which tells him not to do anything. He is later seen running pass by Caesar's location, planning to escape the facility. Chopper managed to acquire enough information of the drug and even got a sedative. As he runs through the hallway, Monet notices him.

Chopper later meets up with Mocha and explained to her about Caesar's deception and using the kids for his experiments and how if Caesar continues to use them, the children will die before they reach adulthood. Mocha remembered her friends promising to each other that when they get older, they will reunite and go on a adventure. The gravity of the situation became clear to Mocha and Chopper promised that he and the rest of the Straw Hat Pirates will save her. While Mocha guards the candy in the Biscuits Room, Chopper attempts the hold back the children. He later enters Monster Point and is fending off the children in Building B. However, Chopper is unable to fight without hurting the children and is beaten down. When the Rumble Ball wears off, the children ran past him and make their way to the Biscuits Room. At this point, Brook, Kinemon, Zoro, Nami, Usopp, and Robin come to his aid. Chopper tells them that he is trying to prevent the children from getting their candy with the aid of Mocha. The group quickly runs after the children to the Biscuits Room. Regardless of Robin's attempt to hinder them, they go after Mocha, who is holding a piece of candy. After Chopper tells Mocha to run, Monet appears and tells Mocha not to keep the candy all to herself and that she should share the candy with the other children.

Chopper and Nami then tends to Robin, but she assures them that her wound is only a cut. Monet tries to attack them when they attempt to run after the children, but Zoro quickly blocks her. After getting hit by Nami's Heat Egg, Monet dives into the snow and stops Nami, Chopper, and Robin from leaving by creating a wall to block their path. An enraged Monet suddenly ensnares Nami and Chopper and prepares to bite Chopper. Nami swiftly move Chopper out of harm's way and Robin uses her Hana Hana no Mi abilities to shatter Monet, saving Chopper and Nami from another attack. Zoro then cut down the snow barrier, allowing Robin, Nami, and Chopper to go after the children.

Chopper, Nami, and Robin then tried their best to keep the berserk children from catching up to Mocha. While Nami and Robin hinder them, Chopper sedates them one at a time. Despite their efforts, some of the children managed to get around the Straw Hat Pirates and catch Mocha. Having no choice, Mocha puts the entire batch of candy in her mouth as Chopper, Nami, and Robin watch in horror. Despite Chopper's pleas, she swallows all the candy. Mocha then begins coughing up blood, due to the serious overdose of the drug. As the children are shocked at what they saw, Chopper yells at them, saying that Mocha sacrificed herself to save them. As they rush to Mocha, Sanji and the G-5 Medical Team finally arrive to help. Some of the Marines have Mocha moved to an examination room so Chopper can tend to her condition. Chopper then compliments Mocha on her bravery and hopes that he can save her.

Nami, Robin, Sanji, the children, and the G-5 with them go on ahead to Building R as Chopper and the Marines with him treat Mocha. Once Chopper is finished with the treatment, they proceed to Building R as well. They later ran into Brook and a petrified Kinemon. Once everyone reach Building R safetly, they board a rail car and make their escape.