Visible crew/equipment: When Freddy falls over the banister onto the stairs near the end, notice the crash mat he lands on. (01:18:55)
Continuity mistake: During the paper cut scene, when Bella is thrown against the table, there are 5 vases of flowers and 3 sets of candles. After she hits the table she lands against one of the vases and knocks the 2nd one to the floor, but the next shot shows only one vase left upright. (00:14:50)
Factual error: The moon is full every night the highschoolers are at the lake house.
Plot hole: Peter goes into Carl's mind to save Catherine. When he's in there he sees the tank with the water nymph. On the tank are strange symbols which provide the FBI with the clue needed to find the latest victim. Makes sense so far. But, go back to the scene just after the FBI have captured the comatose killer and are looking in his basement. The FBI are looking at the contraption that the killer uses to suspend himself over the victim. On the contraption is the same symbol seen later on the water nymph's tank. Why didn't the FBI follow up the symbol then?
Continuity mistake: When the white boy is standing outside the car talking to the gangbanger inside the car, the gangster's sunglasses disappear depending on the camera angle.
Factual error: Federal institutions have strict rules for inmates or patients based on the reason for their incarceration, including substituting metal utensils with safer plastic ones. Despite being convicted of brutally killing his family, Myers is still trusted with a sharp metal fork - resulting in the nurse's death.
Character mistake: Selena Gomez drives into town in a fully restored 1967 Pontiac Le Mans, which is a long box shaped car. However, when confronted with Bill Murray and Adam Driver, Adam Driver complements her on her 1968 Pontiac Le Mans, which is a completely redesigned shorter curved body style. The two look nothing alike.
Continuity mistake: When Mulder and Scully start frantically running from the bees inside the dome Scully is clearly seen untying her belt twice. (01:01:55)