Jake the Dog is a main character in the American animated television series Adventure Time created by Pendleton Ward. He is voiced by John DiMaggio. The character made his debut in the original pilot. Jake is Finn's best friend and adoptive brother. He is a 28-year-old—in "magical dog years"—shape-shifting dog. His magic powers allow him to stretch or shrink any part of his body to any shape and almost any size, ranging from becoming gigantic to becoming incredibly small. Acting as a confidant and mentor to his energetic brother (though he has a tendency to give somewhat questionable advice), Jake has a laid-back attitude in most situations, but loves adventure and will eagerly fight when he needs to. His powers help Finn considerably in combat and transportation, but are also sometimes used as nothing more than jovial forms of expression. Jake is in a relationship with Lady Rainicorn; they have five children together as seen in "Jake the Dad". He met Lady in the pilot episode and is quite skilled at playing the viola, which houses a worm called Shelby.
The character has received largely positive critical reception.
Jake's Stretchy Powers enable him to modify the size, shape, and dimensions of every part of his body. Not only can he stretch and contort himself into highly specific forms, but he can also rearrange his internal organs, and teeth. In "Evicted!" he was able to shrink and move his internal organs and blood into his left thumb. Also in "Jake vs. Me-Mow," he enlarged his liver 51 times a dog his size, preventing him from dying of Me-Mow's poison. One frequent use of his powers is Key Hand, which he uses to pick locks. He has also used his arm as a bow able to accurately shoot arrows at a short distance. As shown in "Mystery Train," he is also able to stretch himself to "create" an entirely new person, as long as they remain connected to him. In "You Made Me!," he is shown to be able to move objects through his body freely when he lets Princess Bubblegum jump into his mouth and then pushes her up through his back. Jake can be stretched by force as seen in "Ocean of Fear," when Finn stretched Jake's ears to avoid making contact with the ocean. Pen Ward has said in an interview that Jake uses his powers lazily and doesn't know their full extent. In "The Witch's Garden," Jake claims to have obtained his powers by rolling around in a magical mud puddle as a puppy, but in an interview Pendleton Ward stated that this is not how Jake got his powers, he just could not remember.