|Introduced in||"Five Short Graybles"|
The Jellyfish was introduced in the episode "Five Short Graybles." Princess Bubblegum placed the jellyfish inside of a machine to produce a tomato. Princess Bubblegum kept it on a plate covered by a little dome. Upon being uncovered, the jellyfish winced, moaned, and covered its eyes, possibly referring to jellyfishes living in darker areas of the ocean. Princess Bubblegum then combined it with a red balloon, thus producing a tomato that was sliced up by Peppermint Butler. The tomato went on the perfect sandwich, which was digested by Cinnamon Bun instantly. Because of these events, the jellyfish is presumed to be dead.
The Jellyfish looks just like a regular jellyfish. His whole body is a light-blue color.