Upon release, this broke the record for the biggest midnight gross of an R-rated movie with $6.3 million, and the biggest opening for a horror movie of all time, earning a total of $41,500,000 in its opening weekend.
For the scare scenes, most of the cast's reactions are spontaneous, such as the cabinet sequence with Kristi. Sprague Grayden was informed that one of the cabinet doors would fly open, but wasn't warned that all of the cabinets would spring open, which provoked a genuine reaction from her.
The preview for this film was banned in some theaters for scaring teenagers and small children viewing PG-13 films.
The trailer for Paranormal Activity 2 used a lot of footage that didn't appear in the movie. This angered many fans, but the directors said "they had to" because of the storyline.
(at around 1h 16 mins) During the climax, immediately following when the power goes out in the house, there is a single, out of focus, frame of Hunter crawling in the street that quickly flashes on and off screen.