Unicorns: A creature probably existed at some point that inspired the modern notion of the unicorn, but I doubt it was ever real as we know it today.
Mermaids: No.
Bigfoot: It’s possible that it started out from a freak encounter with a bear. However, I don’t think it’s real.
Aliens: I think it’s plausible, but I don’t think they’ve visited Earth.
Atlantis: It could be based on a real city that flooded or seemed to disappear into the sea. However, I doubt it is anything like the legends.
Hogwarts: No.
Metahumans: No.
Dragons: I feel like someone had a really terrifying run in with a giant bat, and the story got more out of hand as time went on.
Vampires and Werewolves:
We’re controlling the world! No.
Illuminati: Loosely based in history but has gone way out of control over the years.
Crab people: I’ve seen some at T-Mobile. They’re not as frightening as people make them out to be, but they are annoying and keep talking about how their T-Mobile job will help them take over the world.
Multiple Timelines: I’m really skeptical.
Gay Frogs: No, but they can be transgender,
believe it or not.
Cthulu: No.
Jesuit Conspiracies: No.
Polybius: I get the feeling that this was caused by rumors that got out of hand. It seems like just another creepy “My uncle works at Nintendo” type of story.
I’ll stop there. I’m getting tired.