This weekend, it's going from 160 screens to about 2,000 and it's already hauled in close to $40 million ... and it cost all of $11,000 to make.
Thanks to the movie, actress and waitress Katie Featherston and actor, musician and computer programmer Micha Sloat are suddenly becoming stars.
"Amazing representation and meetings and scripts and so many opportunities that wouldn't have come possibly at all, or at least not this quickly," said Katie.
"I recently signed with an agency and the doors are opening up, and the auditions are coming for great projects, and I'm getting scripts to read," said Micha.
Paramount Pictures is handing out very little footage of the film, opting instead to show moments from the movie with audience reactions to it.
"It came out of nowhere and people just walked in the movie theater without knowing anything and said, 'Oh my god, I wasn't expecting this. This is cool. You should watch it.' And that's the best way to go and experience the movie, in my opinion," said Micha.
"It's really a movie about, you know, where your imagination is what really terrifies you," said Katie. "It sort of re-awakens fears that you may have had as a kid, or fears that you kind of push away, and it really brings those fears to the forefront, and then not only are you scared in the movie but, you know, you're scared when you go home."
"Paranormal Activity" is rated "R." Analysts already think it offers major competition for "Saw VI" this weekend.