Why don't we start off with a bang, and see if we can't do "Doppelganger" up right? As today's theme is those mythological look-alikes and harbingers of doom, you might wish to take the literal path and write about haunting doubles, omens of death and destruction, and phantom warnings.
Of course, there's no reason to stick to literal interpretations only, and this theme leaves plenty of room for twins -- whether they're siblings, simply look-alikes, or people who share some physical characteristic(s) or personality quirk(s) -- for characters confusing other characters with someone else they know and other instances of mistaken identity, and for crossovers between fandoms where one actor/actress appears in both sources.
I'm sure I'm overlooking other twists on the theme, so please, be as literal or figurative as you like, and feel free to turn the theme upside down and inside out; don't forget to shake it to see what else falls out too! Any fandom (RPF or FPF), and any characters/pairings (het, gen, slash, femslash) are welcome!
Please use the following formats (the second is for crossovers) in your requests in order to help the code-monkeys best do their jobs:
Fandom, Pairing, Prompt
Fandom1/Fandom2, Pairing, Prompt
Some examples might be:
LotR, Boromir/Faramir, He kept seeing him everywhere.
The Prestige, Alfred Borden/Fallon, sleight of hand
The X-Files/Once a Thief, Alex Krycek/Victor Mansfield, Gemini
Don't forget that it's one prompt per comment, and you're always welcome to write responses to your own prompts. (Also, you may wish to check out the guidelines here for leaving multiple prompts in a row.)
And remember, if today's theme/prompts aren't for you, the Lonely Prompts indexes are waiting, full of orphaned prompts crying out to be adopted.