An AU story takes an existing cast from a book, show, film, or game and drops them into a rewritten setup, with the classic pitch being a what-if scenario such as a modern-day Pride and Prejudice or Pikachu on steroids3. Changes range from small tweaks, like keeping a dead character alive, to full genre swaps such as a fantasy cast rewritten as coworkers at a coffee shop. Jane Austen's readers have been reworking her Regency plots into new settings for well over a century1.

The tradition of writing AU stories predates the modern internet by decades. Fanlore, the fan-culture wiki, tracks AU-style writing back through the 1920s, when reimagined stories were already appearing in printed zines2. Sequels and retellings kept showing up in fan-focused publications long before AU became a standard category tag online.