Smiley

Smiley, known more commonly as Slime (スライム), is a pet of Caesar Clown. It was created by gathering and compressing the poison gas that spread throughout Punk Hazard. It was kept in the Punk Hazard Burning Lands before being released.

Appearance
Slime, as its name suggests, is a big, dark gelatinous mass. It was described as being bigger than a mountain. It doesn't seem to have a form or shape, however, the mass manifests 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 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. Slime also responds to verbal commands from Caeser and follows them right away.

Abilities and Powers
Slime 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 couldn't escape from it, despite being centaurs. Due to its large size, it is very hard to avoid or escape. Slime 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 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
Slime consumed the Sara Sara no Mi, Model: Axolotl.

History
Four years ago, Slime was created as a result of a chemical weapons experiment going horribly wrong. Caesar Clown condensed the gas from the experiment and created Slime. He then locked up Slime for three years, which brings it to present day.

Punk Hazard Arc
After more and more people appeared on Punk Hazard and caused trouble for him, Caesar eventually did not want to collect bodies for his experiments anymore and instead decided to release Slime. Upon being released, Slime immediately started to spread and move out, killing some of Caesar's men. Later on, it was 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 seperates Ice Land and Fire Land, Slime started to shoot little pieces of himself over to Ice Land, to avoid the water, though all of that happens offscreen. Some parts of it landed on the ship, that the G-5 marines are on. Some Pieces merged together, to form a bigger Slime. After some marines tried to attack the slime with swords and got poisoned in the progress, one of them trys to kill Slime with a flamethrower. Slime is being ignighted at first, giving the marines hope but then goes off in an enormous explosion, destroying the ship and presumly killing the marines in the progress. After the explosion, small lumps of Slime rain down on the battlefield, poisoning some of Caesar's men. Caesar then shows up and explains to the crowd that Slime has been conciously shooting little lumps off himself over the lake.

Later on, Slime was still shooting lumps off himself to the Ice Land side. The pieces that fell into the lake were slowly contaminating the whole water, killing the fish that live in the lake. During Caesar's fight with Luffy, Caesar ordered the Slime pieces to cling themselves to Luffy, in order to create a huge explosion. While the Slime pieces managed to stick to Luffy, the explosion still missed him.

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