The nudibranch seller is a character who only appears in the episode "A Pal for Gary."
She is a light purple fish with light yellow, light green, and black eyes, and black hair. She wears a light blue dress, a red cape, and blue slippers. She looks and talks like a gypsy. She is seen as untrustworthy for her strange appearance and sales of violent creatures, but also cautious as she does not want the nudibranchs to maliciously harm anyone.
In "A Pal for Gary," SpongeBob notices the nudibranchs she sells and immediately gets excited. She tells SpongeBob that they are rare but extremely dangerous. SpongeBob is too amazed by their adorable appearance and takes a green nudibranch, which he later names Puffy Fluffy. She warns SpongeBob that the nudibranchs are violent, and they are aggravated by other pets. She shows an example, with a nudibranch angrily growling at a picture of a cat, but SpongeBob ignores her warnings and leaves with Puffy Fluffy, not even shown paying for him. She makes no other appearances since then.