The concept for The Multiverse sure is amazing. The idea of different dimensions, each representing a different idea being used. It'd be great if someone were to visit them. Okay, let's do just that! But how about we spice this up by having each dimension be the world of an entire work? This is pretty much how a Multiverse Crossover works. This is a kind of crossover that's been done rarely in non-fan works, for obvious reasons. It entails that each world within the Multiverse is actually a world a certain work exists in. A main character, mostly an Original Character, travels throughout these worlds and crosses over into that work. Kind of like a Massive Multiplayer Crossover, only one work is getting the spotlight at a time. Basically all the worlds are in separate Alternate Dimensions or Alternate Universes inside a bigger multiverse. Not to be confused with a Crisis Crossover. A subtrope of Massive Multiplayer Cross Over. See also Intercontinuity Crossover and Mega Crossover. Needs a Better Description. Is it Too Rare to Trope?
- The entire Kingdom Hearts franchise, which has Sora traveling to different Disney Worlds along with Donald and Goofy, although they do travel to Original Worlds like Traverse Town.
- Kamen Rider Decade plays with this. For two thirds of the series, Tsukasa travels to the nine Kamen Rider Worlds, each with their own little kink. However, after Hibiki's world, he winds up in two Original Worlds (Nega World and Diend's World and then pulls off a crossover with Samurai Sentai Shinkenger, Kamen Rider BLACK (and Black RX) and Amazon before finishing off at The World Of The Rider World.
- The Thursday Next novels, in which the protagonist spends substantial time both in individual books' settings and in "Book World", the behind-the-scenes of all fiction, which is structured like a library.
- The Page Master, which shares a similar premise as above.
- Tsubasa Reservoir Chronicle, for CLAMP characters, however, in a twist, they don't go to the actual worlds. Each new universe the main characters travel to features one particular CLAMP manga's characters, albeit in a different setting.
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