Pocket universe

Pocket universes are a type of very small parallel universe sometimes found in science fiction and fantasy. They are sometimes "attached" to a larger parent universe, making them literally pockets of space, but this is not a necessary feature and the name generally just refers to their small size. Small size can be a relative and subjective thing, however; some pocket universes are large enough to contain entire solar systems.

Notable pocket universes include:
*All variations of the Pokèball in the Pokèmon television show.
*Guybrush Threepwood, in the Monkey Island series of computer games, has a very deep pocket where he stores about everything in, ranging from unlimited grog to pianos.
*The Room of Requirement at Hogwarts School of Witchcraft and Wizardry in the "Harry Potter" series
*Bags of holding from Dungeons and Dragons (another type of literal "pocket" universe)
*Demiplanes in the D&D cosmology
*The interior of a TARDIS, from Doctor Who (and, indeed, the pockets of the Doctor's coat)
*The Tesseracted Volume of Dr. Reed Richards, of the "Fantastic Four"
*The "Land of the Lost"
*Hammerspace, a humorous concept used by fans to explain where cartoon characters are able to pull items from "out of nowhere."
*The marbles from "Men in Black".
*The Pocket Universe in post-Crisis "Superman" comics, designed by the Time Trapper as the place from which the pre-Crisis Superboy originated.
*Parasite universes attached to the "Discworld" universe
*The place that the extra mass comes from/goes that Transformers gain/lose when they transform
*The Flat-Space dimensional compression technology in Kurt Wimmer's UltraViolet.
*The night club Pocket D, found in City of Heroes and City of Villains.
*Dark Aether in is a dark version of the planet Aether, located in an alternate dimension.
*The Dunwich Room from the movie Cast a Deadly Spell.
*In the 853rd century DC Universe, as seen in "DC One Million", every city in the Solar System is built into its own pocket universe, leaving the planetary surfaces almost untouched.
*Grandfather's pocket universe in the role-playing game Traveller.
*The Other Zone in "LEXX", an "unstable partial universe" that consists of a shifting metaphorical landscape.
*Photon Nanotrance technology found in Phantasy Star Universe
*Omnyou Mystics from the anime series Magical Shopping Arcade Abenobashi main responsibility was to create an alternative universe for people when something tragic had happened to them. Though not directly explained as a Pocket Universe, it is presumed that the universe is limited to the imagination and knowledge of the Omnyou Mystic who created it.
*Link Books and bubbles from the Myst franchise. The D'ni used books to for many things, refuge, prison, industry, ex.
*Universe Marbles, created by artist Gateson Recko, take the men in black pocket universe and make it a reality.
*"World of Tiers", a series of six books by Philip José Farmer in which humanoids have created a series of small pocket universes which are linked by gates, and populated by persons kidnapped in the far past from Earth.
*In the "Futurama" episode "The Why of Fry", Fry sent the Infosphere into a pocket dimension to keep it from destroying the universe.
*The computer game Chronomaster revolves around adventures in 7 pocket universes.
*The MUD Alter Aeon has a weightless item container named "pocket dimension".
*The MUD ArcticMUD has a rare ring attached to which is a gem that is, itself, a pocket universe into which you can toss items for storage... upon touching an item--a sword perhaps--to the gem, it would vanish it a flash of light. To retrieve the item, the player would think of it and it would reappear.
*In Andromeda (TV series), during the end of the second and beginning of the third season, and in Delenda Est. of the third season, Trance Gemini states the aliens attacking the Andromeda are from a Pocket Universe.
*In the final season Andromeda (TV series), Dylan Hunt, and the rest of the crew of the Andromeda discover that the Seefera System is an artificial Solar System created by the Vedrans and placed inside a Pocket Universe in order to hide Tarn Vedra and to create a braking system for Trance's sun when it returns to the system.
* The surfaces of each world in the popular game Kingdom Hearts.
* Terranigma features a small box which Ark carries with him, that he can climb into to find various rooms including an armory, inventory screen and study.
* In the videogame Chrono Trigger, Lavos has its own pocket universe.
* In Superman continuity the Phantom Zone is often depicted as a pocket dimension.
* In the "Master of Orion" series, part of the story involves the orion race imprisoning their enemies, the antaran race, along with their entire home star system inside what is stated to be a 'pocket dimension'.
* In the "" anime series, rather than into any particular organ, what Kirby consumes seems to enter a "pocket universe" of sorts, depicted with a backdrop of outer space.