The Beauty and the Beast AU I've read twice and love so that's a fairytale I have to stay away from. There's been at least 2 merman AUs, I also remember an Ice Queen story...for space_wrapped, maybe? Any of the Jim or Bones get trapped in their own minds and need Spock to do a mindmeld as Bones or Jim go in to get them back could be Sleeping Beauty or Snow White but I'm going to go with the rule that if they don't outright claim it's based on the fairytale, than it doesn't count. Because then we could say the Pretty Woman based AU was Cinderella and fairytales have just ingrained into so many plots that it could arguably be any story. :P

I'm torn between two right now... One's a fairytale, the other's a Roman myth. But then the Roman myth inspired Beauty and the Beast, so IDK what I'm gonna do.