Character: mystery (spongebob)
Mystery the Seahorse is a female seahorse that SpongeBob adopts in the episode "My Pretty Seahorse." She also appears in the online game "What's Your Bikini Bottom Pet?" and the episode "Gary & Spot."
Mystery is a normal light green seahorse. She is bigger than an average seahorse, which are nearly Plankton's size. She has a swirl that contains a tail.
She has similar mannerisms to a regular horse, eating a lot and neighing.