My friend believes that the Moon landing was faked. When I asked him why, he said something along the lines of "well, there was that Doctor Who episode with The Silence that convinced me". I was like "what? You know that's not real life don't you?" But no, he remains convinced that the Moon landing is faked because of Doctor Who. Or Transformers. I can't remember, but it was something ridiculous like that.
That all world leaders, the Royal Family etc. are shape shifting lizards. Having had the pleasure of David Cameron and the Conservative party running this country for the last few years. I don't know about lizards but I'm pretty sure they aren't human.
This one really blew my mind that someone could believe this. I was driving with a workmate last year and we were talking about something when the subject of racism came up and I told him I wasn't racist. And he asked without a hint of sarcasm, "so what are you going to do when the Muslims take over the world?" That really took me back, I couldn't believe that anyone would seriously think that. But having thought about it, it just seems to be a variation of the old Jews/black people/shape shifting lizards are trying to take over the world thing.