Alternate Universes

Alternate universes are a staple of comic books, and the WW4C is no different. The WW4C also has "pocket dimensions" which aren't entire separate universes but are limited in size.

Here are several alternate universes and pocket dimensions which are known to exist:

• Andalasia: An alternate universe fantasy realm. It's named after the kingdom of Andalasia, but there is presumably an entire world. The only known portal between Andalasia and the WW4C is between a wishing well in Andalasia and a manhole in New York City. The kingdom of Andalasia is currently ruled by King Edward, a native of Andalasia, and Queen Nancy, a native of New York City.
• The Grid: The Grid is a pocket dimension which exists inside the computers at ENCOM, one of the world's largest computer companies. It is unclear whether the Grid exists inside other computers as well. Computer programs in the ENCOM system resemble their human Users, whom the Programs revere. The Grid can be accessed via a teleportation laser in the ENCOM research laboratory.
• Calisota: The alternate universe of Calisota is named after the state of Calisota in its version of the United States. Calisota is a world of talking cartoon animals. It also has its own superheroes, with the town of Duckburg being defended by Gizmoduck and St. Canard being defended by the terror that flaps in the night, Darkwing Duck. The dominant life forms on this world appear to be ducks and dogs, but bears, orangutans, tigers, and other animals are also represented. (Basically, any Disney cartoon featuring talking animals from Darkwing Duck to Duck Tales to Tale Spin to Goof Troop belongs here.)
• The Marvel Universe: The Marvel Universe is a world much like the WW4C but a little bit darker. Heroes in the Marvel Universe aren't always as morally upstanding as in the WW4C, and villains are occasionally outright murderous. The premiere superteam of the Marvel Universe is the Avengers, consisting of Captain America, Iron Man, Thor, and the Hulk. (It might make sense for Spider-Man, the Fantastic Four, and the X-Men to also be in the Marvel Universe, but since those movies are made by other studios, I'm not officially including them.)
• Halloween Town: A pocket dimension in which it is always Halloween. Halloween Town is filled with monsters. There is also a pocket dimension called Christmas Town, in which it is always Christmas. It is unclear whether there are "Towns" for every holiday.
• The Incredibles Universe: This is the home universe of the superteam The Incredibles. It's very similar to the WW4C. The events of other Pixar movies such as Toy Story, Up, A Bug's Life, and Ratatouille are part of the Incredibles Universe.
• Monstropolis: A pocket dimension containing a city where monsters that live under beds and in closets reside. Until relatively recently, the city was powered by the screams of children. About a decade ago, it was discovered that children's laughter was a more efficient energy source. Monstropolis may connect to multiple universes, making it a way to travel between worlds for those who know of its existence.
• Gargoyles Universe: Another universe similar to the WW4C. Like the Marvel Universe, the Gargoyles Universe is less morally clear than the WW4C. Its greatest heroes are a group of gargoyles--magical winged creatures which turn to stone in daylight.
  
• Car World: This is an entire world which is remarkably similar to the WW4C except that it is inhabited entirely by intelligent talking automobiles. (This is a possible origin for Herbie the Love Bug.) It appears to have no humans and no superheroes. Effectively, it is a world of robot cars.

When traveling between worlds, the travelers are typically "translated" into a form which follows the rules of that world. For instance, when various residents of Andalasia came to the WW4C, they became real people instead of animated characters, and the chipmunk Pip lost the ability to speak. Similarly, when Flynn entered the Virtual World, he took on the appearance of a Program. Travelers to Car World are hereby warned.