Throughout Adventure Time show, a lot of imagination zones have been shown. Some of them interfering with the real world in interesting ways. This article contains a list of these imagination zones. The characters with imagination zones include Finn,Ice King and Jake
Ice King's Imagination Zone
The Imagination Zone is a place visited by Ice King. It was first named in "What is Life?" It's a magical place where he can imagine anything he wants. He imagines him and NEPTR enjoying a sunset as father and son.
The Ice King can teleport himself and others into his Imagination Zone, but he goes there involuntarily whenever he's knocked unconscious by Finn too as seen in "What Is Life?" and "Prisoners of Love." It seems that Ice King can't control who goes to the Imagination Zone, because Finn was able to travel there by grabbing the hem of Ice King's robes. The Imagination Zone seems to look like an actual physical place than just something imagined. In "Prisoners of Love," the Cosmic Owl is encountered in the Imagination Zone, telling the Ice King he's a sociopath.
Dark Magician's Brain World
At the ending of "The Enchiridion!," Finn is sent to Dark Magician's "brain world" for a test of his character. It can be the same place, but it seems to function on a similar principle.
Finn's Imagination Land
Finn's Imagination Land is first seen in the episode, "Freak City," Finn appears in it when the song "The Hero Boy Named Finn" starts. He seems to enter it by daydreaming. It was later shown in the episode "Rainy Day Daydream," where Finn enters his mind by focusing on imagining. It's mostly blank because Finn believes that imagination is for those who can't face reality. There are three creatures there, Bellamy Bug, Fairy, and Lyre Player. Finn is shown to know how to control it even though he never uses his imagination, but this could be simply thinking. This was also seen in "Goliad" when Goliad used her psychic powers to enter Finn's mind. Finn tried to fight off what Princess Bubblegum said by thinking of a lot of imaginative traps.
Galaxy of Flavors
"The Other Tarts" starts off with Princess Bubblegum describing a "Galaxy of Flavors" in a scene that resembles outer space filled with floating confections. Later, the Royal Tart Toter, in spite of being blind, deaf, and quite insane, looks like he's drifting away though the same galaxy. For some reason. Lumpy Space Princess can be seen grabbing on a passing doughnut, whether she is really there or just imagined is unknown.
Curiously, title card designer Andy Ristaino said that the title card of "Five Short Graybles" is in the Galaxy of Flavors. But the title card does not seem to fit the episode's story, it seems to show Cuber inside a crystal structure , traveling the Galaxy of Flavors, which contains floating cupcakes, hot dogs and sushi.
Jake's Croak Dream
Jake's Croak Dream and croak dreams in general might be related to this phenomenon, being derived from the deeper parts of the mind like previous examples as well as related with a sight of the Cosmic Owl.