Fanfic prompts, sorted by trope

Every prompt below works with any fandom. Swap in your characters, keep the situation and let the follow-up questions fill in the rest.

Enemies to lovers

Two rivals are assigned the same undercover mission and have to share a single hotel room.
The hero has to ask the villain for help, and the villain enjoys it far too much.
Opposing team captains get snowed in at the same mountain lodge the night before the final.
A duel ends in a draw, so the two of them are bound by a rule that says they must travel together until one wins.
Rival chefs are forced to run the same kitchen for one chaotic week.
The one person who always beats them at everything turns out to be their new neighbor.

Coffee shop AU: the regular who always orders something absurd finally explains why.
Heist AU: the safecracker and the con artist used to be partners, and it ended badly.
Space station AU: the quiet engineer and the loud captain are the last two awake on the night shift.
Bookshop AU: someone keeps leaving notes in the margins of the same secondhand novel.
Royal AU: the bodyguard has one rule, never fall for the person you protect.
Small town AU: the big-city lawyer inherits a bakery and the baker who comes with it.

Two friends pretend to be engaged so one of them can survive a family wedding.
There is only one bed at the inn, and neither will admit they would rather share it.
Stuck in an elevator for three hours with the person they argued with that morning.
Fake dating to win a bet, until both of them start cheating in the same direction.
A long train journey with two seats left, side by side, for nine hours.
A road trip with a broken radio and a lot of things neither of them has said yet.

The character who died in the finale wakes up, and nobody quite knows how to act.
The conversation that should have happened right after the big betrayal.
The quiet morning after the final battle, told from inside the camp.
The time skip the show never showed, five years in five short scenes.
An apology delivered a decade late, at a reunion nobody wanted to attend.
The scene where the side character finally gets to say what they think.

A time loop where the only way out is telling the truth to the one person they avoid.
Soulmate marks appear on the worst possible day, in front of the worst possible person.
A letter from their future self arrives with one instruction: do not trust your rival. Then the rival saves their life.
They wake up married in a timeline where they never met, and the other person remembers everything.
Every reincarnation they meet again, and every time one of them is on the wrong side.
A prophecy says one of them must leave, and they spend a year refusing to decide who.

The crew adopts a stray cat and two crewmates end up sharing custody.
After the war, the survivors open an inn together and nobody admits it's home.
A mentor and their former apprentice, now equals, run into each other at the edge of the world.
Two people keep showing up at the same late-night diner and never exchange names.
A slow burn told through the same holiday, once a year, for seven years.
The team medic has patched up the same reckless fighter so many times it has become a ritual.