Well, I wouldn't say it's a belief. Aliens either exist or they don't. I would say their existence is possible, but contacting or visiting them is less likely. I have little doubt that all those alien abduction stories and crop circles we hear about are bogus.
As for parallel universes, I know physicists work with the multiverse theory, but the concept befuddles me.
There are mentalists and charlatans who do a great job of fooling people into thinking they are psychic, but that's about it.