Nudibranchs are exotic pets featured in the episode "A Pal for Gary" and the online game Gary's Revenge. They are sold at a roadside stand by a gypsy. However, they look nothing like nudibranchs in real life, which look like sea slugs. Nudibranchs are hostile around other pets, especially snails. Puffy Fluffy is a popular-known nudibranch who serves as the main antagonist of "A Pal for Gary," where SpongeBob buys him to keep Gary company while he's at work.
They are fluffy creatures with long eyelashes and dimples. They come in the colors light purple, dark teal, and light green. They all have purple eyes.
They are giant, slimy, angry beasts with multiple tongues with mouths (referencing the movies Alien or Tremors) that correspond with their original colors. They turn into these creatures when around other pets, probably to show that they are the dominant species of that particular territory.
Puffy Fluffy the nudibranch, in harmless form, has a fish-like appearance with a fin and fishtail rather than a slug appearance. However, this appearance can be seen in their evil form, but they still possess a fin.