Prismo

Prismo (voiced by Kumail Nanjiani) 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 "Wake Up," "Jake the Dog," "Is That You?," and "Crossover." He resides in the Time Room, which exists in the center of the multiverse. Booko describes him as "almighty." Prismo is 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 is revealed to be the dream-projection of a sleeping old man in "Wake Up." He sends Finn and Jake to 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 explains he will vanish when his mortal body wakes up, but figures he will reappear once that body goes back to sleep in 1000 years. Unfortunately, the Lich takes advantage of the situation by waking up Prismo's mortal body and reducing it to ash, killing Prismo.

In "Is That You?," Finn and Jake perform a memorial ritual centered around the last of Prismo's pickles. Through a series of time-bending dream sequences involving a past version of Jake becoming the sleeping old man that Prismo resides in the dreams of, Prismo is brought back to life.