Paranormal Activity 3 (2011)

Revealing mistake: While driving the Mercedes to the house of grandma, the gauges on the dashboard show speed is zero and the engine is cold.

Other mistake: While Dennis is editing one of the video tapes, there's one on a table labeled "89" even though the film takes place in 1988.

Factual error: During the sleepover in the tent Dennis gives the girls M&Ms to snack on. If you look closely you can see one of the girls eating a blue M&M. These didn't hit the market until around 1995, a full 7 years after this movie takes place.