Most of the scenes in the trailers are not in the actual movie which angered many fans of the series. According to Inside Pulse, the production team behind this had enough leftover footage to assemble two completely different versions of the same movie; fifty-percent of the footage was what they used to create the TV spots and theatrical trailer.
(at around 5 mins) Towards the beginning of the film, Julie takes a picture of young Katie standing in the driveway shortly before a group picture is taken. The photo being taken appears in both Paranormal Activity (2007) and Paranormal Activity 2 (2010) as an indication that the demon has started haunting them.
(at around 4 mins) The scene with Kristi's loose tooth was real. "Little girl shows up on set and says that she's got a loose tooth," Ariel Schulman said. "We say, 'Film it, work it into the scene.' Can't fake that."
The highest grossing film in the Paranormal Activity series.
The camera seen on screen during most of the film is actually a tiny Hi-Def camera hidden inside the body of a VHS camcorder. For the first few weeks of shooting, Smith did not have a viewfinder to see what his footage would look like. "So what they had to do was they built, or they put in a screen, a little monitor in the viewfinder that was transmitting the video that it was recording in the body of this old VHS tape into this monitor. So I was basically watching a little monitor in the viewfinder, and it was like, week six when they figured that out."