Internet Rule 50: Every franchise will eventually have a
crossover with every other franchise in some form. In other words, if it hasn't happened yet, someone's probably working on it now.
This trope includes any type of contact between franchises, whether it be physical or merely conceptual. See the image, which incorporates characters from
My Little Pony Friendship Is Magic and the graffiti meme from
Silent Hill in a single piece of artwork (
Friendship is Magic, in fact, may be the single most infamous example of this trope in recent memory, having been crossed with everything from
Super Mario Bros. to
Pokémon to
King of the Hill to
The Amazing World of Gumball to
even Fallout). Another example is
Sailor Moon meeting
World of Warcraft, two franchises with very different atmospheres.
The resulting crossover may be
art or
fiction. It may be a delightful surprise, like finding out how well chocolate and peanut butter go together, or it may turn your stomach.
This can apply to a
Common Crossover,
Mega Crossover, or even a
Massive Multiplayer Crossover but not a
Crisis Crossover which features characters from the same universe.
Note that
Rule 34 refers to prurient versions of single franchises, while
Crossover Ship refers to romantic crossovers only.
Rule ⑨, however, has
has its own page.