An extradimensional being is a type of hypothetical entity in a dimension beyond our own. Such beings are common in science fiction, fantasy and supernatural fiction.
Science fiction
Implementation of dimensional portals
In the Star Trek universe, wormhole theory states that if a section in the fabric of spacetime joins together with another section of spacetime, a direct connection can be made between the two, allowing speedy travel between the two spacetime coordinates. Black holes are one such way of stretching the fabric of spacetime; so it's theoretically possible to create wormholes using a pair of singularities, at least in the fictional universe of Star Trek. The NASAWeb site has a somewhat dated article called "The Science of Star Trek", by physicist David Allen Batchelor, which considers some of the implementations in Star Trek. He says it's "the only science fiction series crafted with such respect for real science and intelligent writing", with some "imaginary science" mixed in; and considers it to be the "only science fiction series that many scientists watch regularly", like himself. He says it's "more faithful to science than any other science fiction series ever shown on television".
In movies and TV shows
Akira
Rick Sanchez
In literature
''The Time Machine'' (H. G. Wells)
The Time Machine by H. G. Wells describes time travelers as interdimensionally capable. The protagonist describes the passing of time, and also treats it as if it were a spatial dimension. This is exactly how H. G. Wells devises the time machine mechanism in this particular work of fiction. H. G. Wells supposes that if time could simply be treated as space, then time machines would indeed operate correctly. In this case, the H. G. Wells definition of a time traveler must be equivalent to that of an interdimensional being – an entity capable of traveling through unusual dimensional rifts that few other entities can enter. From H. G. Wells' Work: 'Clearly,' the Time Traveller proceeded, 'any real body must have extension in four directions: it must have Length, Breadth, Thickness, and—Duration. But through a natural infirmity of the flesh, which I will explain to you in a moment, we incline to overlook this fact. There are really four dimensions, three which we call the three planes of Space, and a fourth, Time. There is, however, a tendency to draw an unreal distinction between the former three dimensions and the latter, because it happens that our consciousness moves intermittently in one direction along the latter from the beginning to the end of our lives.
by Douglas Adams describes that mice are 'merely the protrusion into our dimension of vast hyper-intelligent pan-dimensional beings.' The old man, Slartibartfast, from Magrathea told the protagonist, Arthur, that the planet he lived on, Earth, 'was commissioned, paid for, and run by mice.' and that the mice were furious when it was destroyed.
An additional fictional work that does include universe dimensionality of some sort includes the Buffy the Vampire Slayer series, according to a particular academic source.
