Paranormal Activity Prank
I loved the first Paranormal Activity movie. It was unlike anything I'd seen before and gave me a lot of genuine 'scares'.
Of course they had to follow it up with a couple of less than great sequels and there will be more to come since it made money.
Despite people knowing that the movie isn't real, doesn't mean people don't believe in the paranormal. So a couple of pranksters decided to capitalize on that fear and scare the crap out of their friend!