The TVA (Time Variance Authority) is an organization that monitors and protects the multiverse from disruptions caused by time travel.

In Ubik, Dick explores the idea of a shared consciousness and the existence of multiple realities.

The Upside Down is a parallel dimension that is dark, dangerous, and inhabited by monstrous creatures.

The Multiverse in DC Comics is a collection of infinite parallel universes, each with its own unique set of characters and storylines.

Borges is known for his short stories that explore the themes of infinity, time, and the nature of reality.

The Commission is a mysterious organization that regulates the flow of time and prevents paradoxes from occurring.

In Neverwhere, Gaiman tells the story of Richard Mayhew, a young man who falls through a crack in reality and finds himself in London Below, a hidden city beneath London.

The Portal Gun is a device that allows Rick to create portals to other dimensions, enabling him and Morty to travel to different worlds.

Everett is known for his Many-Worlds Interpretation of quantum mechanics, which posits that every possible outcome of a quantum event exists in a parallel universe.

The Secret Wars was a major crossover event in Marvel Comics that resulted in the destruction of the multiverse and the creation of a new one.

In A Wrinkle in Time, Meg Murry and her brother Charles Wallace travel through time and space to rescue their father, who has been trapped on another planet.

The STAR Labs Particle Accelerator was responsible for creating the wormhole that allowed Barry Allen to travel to Earth-2.

Moorcock is known for his Multiverse Cycle, a series of novels that explore the idea of a multiverse where different versions of the same character exist in different worlds.

The Fringe Division is a special unit within the FBI that investigates cases related to alternate universes and fringe science.

In The Lion, the Witch and the Wardrobe, four children travel to the magical land of Narnia through a wardrobe.