The bullet hole in the back of Charles Brady's shirt disappears.
Officer Horace shoots the vase with yellow flowers twice
During the chase scene, the odometer in the Trans Am is shown twice and the second time, the mileage is less.
When Tanya is trying to start the police car in the end so she can get away while Mary Brady is on fire, Mary leans against the car to shout at Tanya and leaves fire on the hood after sliding off. When Tanya finally puts the police car in reverse the fire is still there, but in the next shot when she stops the car going backwards barely 10 feet the fire is no longer on the hood.
When officer Andy loses the Trans Am, he stops and gets out of the police car, leaving his door open, and walks towards the front of the car. He is looking down the empty road, and the driver's door is closed but still ajar. When Clovis (the cat) is looking at the invisible Charles, the driver's door is open. And when Andy gets back in the car, the door is open.
Horace is killed when Mary stabs him in the back with a cooked cob of corn. Raw or cooked, a cob of corn is nowhere near strong enough to pierce through a human spine.
In the beginning where Charles is cutting his arm, you can clearly see the outline of the blood patch he is actually cutting.
When Mary grabs the 'cop' and puts him on the fence, it is obviously a dummy.
The mountains of California are everywhere in this movie, yet it supposedly takes place in rural Indiana, one of the flattest states in the U.S.
Southern California looks nothing like Indiana. Even Brown County, IN give Appalachia vibes but not San Gabriel. Not even close.
When Tanya takes pictures through the SLR camera in the cemetery, she should have seen Charles in his true form since the image in an SLR viewfinder is bounced off a mirror.
In the very first shot of the movie, the two police officers talking to each other and pass a police car and you can see a boom mic reflected off the back of the police car as they talk.