Prismo is a Wish Master who is the manifestation of an old man's dream. First mentioned in "The Lich," he plays a major role in the episodes "Finn the Human" and "Jake the Dog." He resides in the Time Room, which is found in the center of the multiverse. Booko describes him as "almighty." Prismo was apparently good friends with a number of cosmic-level characters in the Adventure Time universe, including the Cosmic Owl, Party God, Death, and Grob Gob Glob Grod, all of whom were seen at one of his Time Room parties.
He was revealed to be the dream-projection of a sleeping, old man in "Wake Up." He had Finn and Jake retrieve his mortal body to wake him up, thereby committing a cosmic crime and summoning a Citadel Guardian to take them to the Citadel to find Finn's human dad, Martin. Prismo explained he would vanish upon his mortal body waking up, but figured he would reappear once that body went back to sleep. Unfortunately, the Lich took advantage of the situation to reduce Prismo's mortal body to turn into ash once he awakened, killing Prismo.
Appearance
He looks like a very large, pink shadow of a human and can move in a similar fashion to a shadow. He has light blue eyes.
Personality
Prismo is a very considerate and friendly being, demonstrated several times throughout the episodes he is in. He gives Jake advice about what wish to make, and throws parties in his Time Room. Despite his omnipotent power, he is far from being aloof and indifferent towards mortals and is in fact the exact opposite. He is generally nice to the people he meets, as shown when Finn and Jake first enter the Time Room, and is even willing to sacrifice himself for the needs of his friends, demonstrated when he told Finn and Jake they could "kill" him (wake up his corporeal form) in order to reach the Citadel.
Abilities
Prismo can grant any being in the multiverse one wish. Once the wish is granted, the wisher is transported into his/her wish-altered reality. These wishes are powerful enough to change timelines and create or destroy worlds. However, unless worded very specifically, his wishes usually have an unpredictable twist, since the wish often changes the timeline, or brings in an unwanted element.
Prismo can also create material items for himself and others without it counting as a wish, like food and a hot tub, as seen in "Jake the Dog" and "Wake Up."
Relationships
Cosmic Owl
Prismo is seen with the Cosmic Owl, and the two appear to be friends. The Cosmic Owl comes to hang out with Prismo in the Time Room while Jake is there, and he implies that he has done this in the past. In "Wake Up," the Cosmic Owl leaves Prismo's time room in a hurry before Prismo's mortal body is destroyed (thus killing Prismo), possibly implying that since the Cosmic Owl knows how and when people will "croak," he wanted to leave before it happened as not to see his friend die.
Jake
Prismo grows close to Jake while Finn is suffering the consequences of his wish, and he helps Jake resolve the universe by telling him what to wish for. Jake says that Prismo is a "strong number three on [his] Cool Guys List." Prismo later sends Jake a jar of pickles with a note, which says that he wants to hang out with Jake more. Jake insists that he has to get Prismo a girlfriend. In "Wake Up," Jake tells Prismo that he always smiles around him, with Prismo telling him he feels the same. Later, when The Lich kills Prismo's mortal body (with his breath), Jake becomes furious and grows large and muscular, declaring that he will kill The Lich for killing Prismo.
Trivia
Prismo has his own pickle brand, "Prismo's Homemade Artisinal Pickles," as seen in "Jake the Dog."
Prismo is profiled as a "wish master" in the T.V. Guide description of "Finn the Human."[1] Prismo also refers to himself as such in "Wake Up."
Prismo says that he gets out of relationships because he does not want to bother about discussing what to eat for dinner every night.
Prismo was a lighter shade of pink in "Finn the Human" than in "Jake the Dog."
Prismo can create anything he wants with colored magic cubes, such as a jacuzzi, cheesy crackers, pickles, a remote, and an egg.
As stated in "Finn the Human," once the Lich made his wish, he was transported to his wish-altered reality. Since Jake made his wish in the next episode, Jake was transported to his wish-altered reality, though Prismo does not point this out. This means that the next episodes are held in Jake's wish-altered reality, with the Lich in his reality.
In "Wake Up," the Lich wakes Prismo's humanoid body up, causing his wish master form to disappear. His humanoid form is then killed by the Lich, preventing his wish master form from returning.
In "Wake Up," Jake touches the "P" on the note Prismo left him at the end of "Jake the Dog," which transports him to the Time Room.
Prismo was the dream of an old man, and Prismo's dream form hung out with the Cosmic Owl, the Cosmic Owl appears in the dreams who are gonna die, so his death was technically predicted.
It could be inferred that Prismo has a son somewhere in the Multiverse: after being abruptly awoken by The Lich, Prismo asks if he is his son.
Cultural references
Prismo twice refers to the classic horror story "The Monkey's Paw" when attempting to explain the unintended perversion of the wish's outcome on reality.
Prismo is similar to a genie in that he is an immortal being who can grant wishes.