What Does Crossover Mean?
Fic TypeA fic that combines two or more separate canons, bringing their characters and worlds into contact — the detective meets the wizard, the starship picks up the time traveler. Distinct from a fusion, where one cast is placed inside another's world.
Crossover in Practice
Crossovers are as old as fandom itself, born from the simple itch of wondering how characters from different universes would get along, fight, or fall in love. The craft challenge is reconciliation: merging two canons' rules, tones, and timelines into one coherent story, which ranges from trivial (two procedurals share a case) to heroic (hard sci-fi meets high fantasy). Fandom distinguishes the true crossover, where both worlds exist and collide, from the fusion, where one canon's characters are reimagined inside the other's setting. Crossover ships pair characters who have never technically met, a category with its own devoted following. AO3 lists every involved fandom in the work's fandom tags, which is how readers stumble delightedly into them.
Example usage
"The crossover treats both magic systems with total respect, and watching the two geniuses argue is worth the price of admission."
Related Terms
Fusion
An AU that pours one canon's characters into another canon's world — the crew reimagined inside the Hogwarts system, the detectives in the Pacific Rim universe. One cast, another world's rules.
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Crack Ship
A pairing so unlikely it is essentially a joke — characters who never met, have no canon connection, or come from wildly mismatched contexts. Shipped for fun, chaos, or the challenge of making it work.
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AU (Alternate Universe)
Short for Alternate Universe: a story that deliberately changes fundamental facts of the canon setting — the time period, the world's rules, or the characters' circumstances. Coffee shop AUs, no-powers AUs, and modern AUs are classic examples.
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Canon
The official source material and everything established as true within it — the events, characters, and facts of the original book, show, game, or film. Fanfiction defines itself in relation to canon: following it, bending it, or discarding it.
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