Fanfic AU ideas, with a note on what makes each one work

What makes an AU work

An AU works when the new setting puts pressure on the relationship you care about. The characters should be recognizable within a page, even with new jobs and new clothes. If you could swap in any two names and nothing would change, the fic has stopped being fanfic.

For each idea, work out two things: what the setting forces the pair to do together, and which core trait of each character survives the move. A fiercely loyal knight becomes a fiercely loyal firefighter. A schemer is still a schemer in a ballroom, just with better gloves.

The big classics (coffee shop, heist, bookshop, royal bodyguard and friends) are already on the prompts page, so this list leaves them out.

Modern AUs

Everyday settings, where the drama has to come from the people because nothing is exploding.

• Wrong number AU: a misdialed text turns into months of late-night messages between strangers. It works because they meet as minds first, which suits characters who are guarded face to face.
• Flower shop and tattoo parlor AU: two shops share a wall, a back alley and a feud over parking. It works because both jobs put each character's care and patience on display.
• Accidental roommates AU: a lease mix-up leaves two people who can't stand each other sharing a flat and one bathroom. It works because forced proximity turns into routine, and routine is where affection sneaks in.
• Rival wedding planners AU: two planners from competing firms are hired by the same couple, who refuse to pick one. It works because the whole setting is about love and both leads are professionally cynical about it.
• Dog park AU: two people whose dogs adore each other keep getting dragged into conversation every morning. It works because the dogs do the flirting the humans won't, which suits stubborn pairs.
• Touring band AU: the lead singer and the sound engineer spend eight months on one bus. It works because fame gives one of them a public mask and the other a backstage view of what is under it.
• Office AU: two managers of rival departments are forced to share one project and one tiny meeting room. It works because office politics shrink any canon power struggle into something petty and funny.

Historical and period AUs

Older settings bring rules, and rules are wonderful for a slow burn.

• Regency AU: two characters are pushed toward a match neither wants during one social season. It works because strict manners make a held glance or a gloved hand feel enormous.
• Western AU: a sheriff and the outlaw she's meant to bring in have to cross the territory together so he can testify at a trial. It works because a lawless setting tests whether a character's code is really theirs.
• Age of sail AU: a navy officer and the privateer he was sent to capture wash up on the same island. It works for enemies, because rank and law sink with the ship.
• Jazz age AU: a club singer and the detective investigating the club's owner. It works because everyone has a secret and a cover story, which suits characters who lie well.
• Fairy tale AU: cast your pair in a fairy tale shape, like the cursed one and the person who stays anyway. It works because the reader already knows the structure, so all the attention goes to the characters.

Speculative AUs

Ghosts, gods and machines: settings that turn a feeling into a literal rule.

• Ghost AU: one of them moves into a flat haunted by the other, who is extremely annoyed about it. It works because they can talk but never touch, which turns the whole fic into longing.
• Witch and skeptic AU: a village witch who runs an apothecary meets the new doctor who thinks it's all nonsense. It works because the values clash can soften without either side being wrong.
• Cyberpunk AU: a fixer who trusts nobody and an android built to be trusted. It works because it asks what being human means, which gives depth to any character with a hidden past.
• End of the world radio AU: a lone radio operator broadcasts every night, and one stranger answers. It works because hope becomes the romance, and meeting in person becomes the big set piece.
• Gods and mortals AU: one character is a small, forgotten god of a crossroads and the other is the last person still leaving offerings. It works because devotion is literal, and the power gap is a question the fic has to answer.

AUs that bend the story itself

These keep the canon world and break one of its rules.

• Role reversal AU: the hero and the villain swap places from the first scene. It works because it shows how much of each character was choice and how much was circumstance.
• Hanahaki AU: one-sided love grows flowers in the lungs until the feelings are returned or surgically removed, love and all. It works as pure angst, because it asks whether loving someone is worth the pain. Tag it for illness.
• Theatre AU: two leads who can't stand each other are cast as lovers in a long-running play. It works because the stage lets them say every line they would never say offstage, night after night.

How to pick one for your ship

Start from the pair's central dynamic. Rivals want competition and close quarters: the office, the wedding planners, the island. Pining pairs want distance or rules, like the wrong number, the regency season or the ghost. Pairs built around a big secret want masks, so try the jazz age or the touring band.

Then decide how much canon you keep. Some AUs keep the backstory almost intact and only change the scenery. Others rebuild from scratch. Say which in your notes so readers know what they are getting. For situations instead of settings, there are fifty more in fanfic ideas.

Writing an AU without losing the characters

• Write a one-line translation for each character: who they were in canon, who they are here, and the trait that did not change.
• Keep one canon detail on purpose, like a scar, a phrase or a habit. Readers love spotting it.
• Skip the three pages of world explanation. Drop the reader in and let the setting show through what people do.
• Tag the AU type by name. Readers search for these, and a clear tag is how they find you.
• Test the premise before you commit. The AI fanfic generator takes an AU setting and a pair and asks what carries over, which is a quick way to see if the idea has legs.

Questions