Fusion — Tag Meaning
Merges canons instead of introducing them: one fandom's characters are poured into another fandom's world, replacing or becoming its inhabitants — the cast attends Hogwarts as students, pilots the Jaegers themselves, lives in the daemon-having universe natively. Unlike a crossover, the second canon's characters usually don't appear; only their world does.
What to Expect From "Fusion" Fics
One cast wearing another universe's premise; the appeal is recasting, not meeting — who would they be if they'd been born there?
How to find Fusion fics on AO3
On AO3, click any tag to see every work that uses it, then refine with the "Filters" sidebar — combine it with your fandom or ship, set a rating, or exclude tags you don't want. See our AO3 filtering guide for the full walkthrough.
Browse "Fusion" works on AO3Related Tags
Crossover
Brings two or more separate canons into contact: the detective meets the time traveler, the starship picks up a wizard, two unrelated casts discover they share a city. In a crossover both universes remain themselves — characters keep their own histories and rules, and the story's spark comes from worlds colliding rather than merging.
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Alternate Universe - Hogwarts
Enrolls a non-Harry Potter cast at Hogwarts School of Witchcraft and Wizardry, complete with house sortings, Quidditch tryouts, and detentions in the Forbidden Forest. Half the fun is the sorting debate itself — fandoms argue passionately about which character belongs in Slytherin — and authors often map canon dynamics onto inter-house rivalry.
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Alternate Universe - Daemons
Borrows the daemon concept from Philip Pullman's His Dark Materials: every person's soul lives outside their body as a talking animal companion that settles into a fixed form at adulthood. Fandoms adore the device because choosing each character's daemon is an act of interpretation, and touching someone else's daemon is the setting's ultimate intimacy taboo.
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Crossovers & Fandom Fusions
The canonical umbrella that AO3's wranglers use to gather both traditions — worlds meeting and worlds merging — under one filterable roof. Browsing it surfaces the full spectrum, from cameo-sized crossovers to total fusions, which makes it the right entry point when you want multi-fandom work without committing to one mechanism.
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More Crossovers & Fusions Tags
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