Cake

Cake the cat is the gender (and species)-swapped version of Jake the dog. She can stretch, bend, and morph her body like Jake. Cake travels with Fionna, who is the female version of Finn. Both were created by Adventure Time character designer Natasha Allegri. Lord Monochromicorn is Cake's boyfriend, just like Lady Rainicorn is Jake's girlfriend. As a cat, she also possesses the ability to see in the dark, while Jake has a keen sense of smell. It is also shown that when ever danger is around, the fur on her tail stands on end or "frizzes out". Natasha announced that Cake will appear alongside Fionna in an upcoming season 3 episode 6. She is scared of Marshall Lee who is the male version of Marceline.

Appearance
Strangely enough, she doesn't look much like Jake, aside from their body proportions. She has white eyes in which the pupils become circular if surprised, excited, shocked, or scared. She has a cat muzzle and a small nose (compared to Jake's), cat ears, white fur with many coffee colored spots, and a large bushy tail.

Trivia

 * Cake's name is a play on Jake's name, and is also based on Natasha's cat, Pancake.
 * She's the species of animal that most people see as the opposite of dogs: cats.
 * Her eye colors are an inverted version of Jake's; while Jake's eyes are black with white irises, Cake's eyes are white with black irises.
 * Cake may know Morse Code in order to speak to Lord Monochromicorn, similar to how Jake knows Korean in order to speak to Lady Rainicorn.
 * Cake's tail frizzes when there's trouble.
 * Roz Ryan (The voice of Cake) has been in many other shows like The Marvelous Misadventures of Flapjack as Bubbie the Whale, Thalia in Disney's Hercules & Witch Lezah in The Looney Tunes Show.
 * As seen in the comics above, she might have defeated the Rat King, because the last head that she had brought had crown.