Nudibranchs are extremely vicious and unfriendly around other pets, especially sea snails. Puffy Fluffy is a well-known nudibranch who serves as the main antagonist in "A Pal for Gary," where SpongeBob buys him to keep Gary company while he is 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 that correspond with their original colors. They turn into these creatures when around other pets.
Puffy Fluffy, 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.
Its harmless form looks similar to a piranha.
Their multiple tongues with mouths are a reference to the films Aliens and Tremors.