Dolphin

The Dolphin is an aquatic mammal who makes her appearance in "Memories of Boom Boom Mountain." She first appears having a tea party with Jake. Later, she appears at the end of the episode when she has fallen in love with him. When Jake thinks of it as a problem, Finn says it is the total opposite of a problem. This is promptly followed by a scene of Finn and Jake riding her across the water. Jake afterwards explained to the Dolphin that he has a girlfriend(Lady Rainicorn), and then she killed herself.

Appearance
She is a dolphin and at one point has a cat on her head.

Trivia

 * It is unknown where the cat came from.