TedStixon

Continuity mistake: When Elise is investigating her old bedroom, a shadow walks up behind her, and she turns around and shines her flashlight on it, and the shadow turns into a coat on a hanger. In the first shot, she's standing sideways looking at the coat. In the next shot, she's instantly turned 90° and is fulling facing the coat.

TedStixon

Continuity mistake: When Specs makes the bad joke about the "Winneba-ghost," Tucker goes from looking forward at Elise to looking sideways at Specs instantly between cuts. Then, in the very next shot, Specs goes from looking at Ted to looking at Tucker and Elise instantly between cuts.

TedStixon

Continuity mistake: When Ted unlocks the locked room (after Specs helps him move the table), Specs walks behind Tucker. In the very next shot, he's back in front of Tucker.

TedStixon

Continuity mistake: When Specs helps Ted move the table covered in bibles, Ted slides one of the bibles under his right armpit to hold it. But in the very next shot, suddenly the bible is in his left hand.

TedStixon

Continuity mistake: When Tucker is demonstrating his voice-activated lights, the way he has his arms outstretched changes between cuts. (In the closeup, they're fully extended, but in the wideshot, they're only partially extended).

TedStixon

Continuity mistake: After Elise wakes up, the way she pets her dog Warren changes between cuts. (She has both hands on him, but in the first shot she's petting him with her right hand, and in the next shot her left).

TedStixon

Continuity mistake: After young Elise is locked in the basement, she cranks the generator to turn lights on. Instantly between cuts, the crank rotates about 180°, going from being all the way down to all the way up.

TedStixon

Continuity mistake: When Elise's father is taking her down to the basement and he screams "I punish people for a living!" watch Elise's mother. Her hands (which were down by her waist in the previous few shots) are instantly up by her neck when it punches in to a closeup of her crying.

TedStixon

Audio problem: In the opening scene, when Christian asks young Elise "How did you know that?!" after the talks about the man who was just executed, his mouth isn't moving. (True, he's out of focus in the background, but he's not speaking).

TedStixon

Continuity mistake: In the opening scene, when we first see Gerald sitting down, there's a lamp on the table next to him. There is no visible cord coming out of the lamp. A few shots later, suddenly a cord appears on the table, coming out of the lamp. (It can be seen next to the yellow plate).

TedStixon

Trivia: The only film in the franchise to not use the series' trademark screeching violins over the opening title card. In addition, it's the only sequel in the series to use a subtitle instead of "Chapter" and a number, with the previous two films being referred to as "Insidious: Chapter 2" and "Insidious: Chapter 3."

TedStixon

Trivia: The town in which the film takes place is briefly mentioned to be called "Five Keys." Which is a bit interesting, as the villain is a demon who has keys emitting from his finger tips, thus literally having "five keys" per hand.

TedStixon