A few years ago I found myself going out with a full blown conspiracy theorist. Everything was questioned and generally the Jews were to blame. Her whole family were involved in it too.
(She was hot, and I was young

)
My favourite theory was that there was an invisible planet on the periphery on our solar system. I think it was supposed to be a giant space ship monitoring earth and her people. The ship was under the command of the galactic federation of species (all very earth-like species. Monkey people, dolphin people, lizard people) captained by a Lion-man.
Come the time that the earth would be destroyed, this galactic NATO would come down and save the believers in Planet X and welcome them into their club.
She believed this 100%.
I bailed when the crazy got too crazy. However, conspiracy theorists make up a sizeable sub culture. So much so that you can't mention 9/11 without getting the inside job routine.
So what's your favourite or craziest conspiracy theory that people you've met believed in?
I'd ask you what's the craziest theory you believe in but that would hardly work