Smiley

Smiley (スマイリー), known more commonly as Slime (スライム) and also as Shinokuni (シノクニ), was a pet of Caesar Clown. It was created by gathering and compressing the poisonous H2S gas that spread throughout Punk Hazard. It was kept in the Punk Hazard Burning Lands before being released.

Appearance
Smiley, as its other name "Slime" suggests, is an enormous gelatinous mass that was compared to a mountain in size. It does not seem to possess a distinct solid form or shape, though the mass does manifest a head with a mouth and two small, light-colored eyes. It also constantly emits some kind of toxic vapor.

Personality
It seems to have little or no mind or understanding of its actions, as it continuously moves forward after being released and killed some of Caesar's men in the process. It knows, however, that it is weak to water and figured out a way to avoid it, by propelling little parts of itself over the body of water. Smiley also responds to verbal commands from Caesar and follows them right away. However, Smiley sometimes ignores Caesar if it is interested in something.

Abilities and Powers
Smiley constantly emits some kind of smoke or vapor, which poisons people that inhale it or touch it. It is also very corrosive, causing great pain on its own. Despite its composition, it appears to move faster than the average person, as some of Caesar's men could not escape from it, despite being centaurs. Due to its large size, it is very hard to avoid or escape. Smiley also appears to be immune to extreme heat, as it could freely move over the scorching ground in the Burning Lands without any trouble. It can also shoot pieces of itself called Smilies (スマイリーズ) in order to cross a lake or other body of water, as it is weak to water. Even though it is immune to extreme heat, setting its body directly on fire will cause it to explode violently.

Devil Fruit
Smiley consumed the Sara Sara no Mi, Model: Axolotl, which allows the user to transform into an axolotl. It is also what gave Smiley life and sentience. However, given its unique composition, it is very likely that it can only assume a hybrid form and not a full-beast form.

History
Four years ago, Smiley was created as a result of Caesar detonating his illegal chemical weapon of mass destruction experiment when Vegapunk attempted to dismiss him. One year later, when Caesar returned to the destroyed island, he condensed the H2S gas from the experiment and "fed" it the Sara Sara no Mi, Model: Axolotl, thus creating Smiley. He then locked up Smiley for three years, which brings it to present day.

Punk Hazard Arc
After the Straw Hat Pirates and the G-5 Marines appeared on Punk Hazard and caused trouble for him, Caesar eventually lost interest in collecting bodies for his experiments and instead decided to release his pet, Smiley. Upon being released, Smiley immediately started to spread and move out, killing some of Caesar's men. Later on, it is seen advancing further towards the Punk Hazard Ice Lands, where it was noticed by Zoro but mistaken for a mountain.



Upon reaching the lake that separates the ice and fire sides, Smiley started to shoot little pieces of itself over to the ice side to avoid crossing the water. Some parts of it landed on the ship that the G-5 Marines are on, merging together to form a bigger Smiley. After some Marines tried to attack the slime with swords and get poisoned in the progress, one of them tries to kill Smiley with a flamethrower. Smiley, while ignited, at first gives the Marines hope, only to detonate in an enormous explosion, destroying the ship and presumably killing the Marines in the progress. After the explosion, small lumps of Smiley rain down on the battlefield, poisoning some of Caesar's men. Caesar then shows up and explains to the crowd that Smiley has been consciously shooting little lumps off itself over the lake.

Later on, Smiley was still shooting lumps off itself to the ice land side. The pieces that fell into the lake were slowly contaminating the water, killing the fish that lived in the lake. During Caesar's fight with Luffy, Caesar ordered the Smiley pieces to cling to Luffy, in order to create a huge explosion. While the Smiley pieces managed to stick to Luffy, the explosion still missed him.



Back near the lake, a large amount of Smiley's body had managed to surround Zoro, Brook, and Kin'emon despite the former two's efforts to hold it back. Finding themselves unable to attack the poisonous mass, Smiley almost overcomes them before Kin'emon reveals his Fox Fire style swordsmanship, which ignites and detonates Smiley pieces in the immediate area, but contains the explosions.

Smiley is then seen during Caesar's Den Den Mushi broadcast chasing after Zoro, Sanji, Brook and Kin'emon. Upon venturing further inland, the group come across a large piece of wrapped candy being pulled by Caesar's subordinates. Without hesitation, and completely ignoring Caesar's order to wait, Smiley devoured the candy whole in a single gulp.

It then "died" as it collapsed back into its original gas form, only this time, the gas is much deadlier because of the effects of the bait: instead of poisoning its victims, it petrifies them. A nearby apple is seen transforming into a Devil Fruit, an indication of Smiley's "death".

Trivia

 * Smiley's "death" is a reference to a pyroclastic flow, a fast moving current of gas and ash which is the result of a volcanic eruption.
 * Smiley is the first Zoan Fruit user to die.
 * Even if it's not a "living being", Smiley is dead. If this is due to the vanishing of the Devil Fruit from his body or vice versa, it's still unknown.