Meme!

Snaffled from a couple of you - this one sounds like fun ^_^

The Hypothetical AU Meme: Take any one of the fandoms you know I
write in (or think I should), and give me a type of AU (space opera AU,
pirate AU, superhero AU, Ancient Rome, etc). I will then explain what
story from your chosen fandom I would write for your chosen type of AU