Jake
Jake the Dog is Finn's best friend and dog with magic powers that allow him to stretch or shrink to any shape and almost any size. He is 28 years old (in magic-dog years). Acting as a confidante and mentor to his energetic pal (though he sometimes gives somewhat sketchy advice), Jake has a laid-back attitude in most situations, but loves adventure and will fight when he needs to. He is the boyfriend of Lady Rainicorn, whom he met in the pilot. His powers help Finn considerably in combat and transportation, but are also sometimes used as nothing more than jovial forms of expression. He is also shown to be quite skilled at playing the viola. He is the deuteragonist of the show.
