Revealing mistake: In the scene when Christine smashed repeatedly into the silver Camaro at the gas station, there is no motor in the Camaro. The hood of the Camaro gets knocked off the hinges and is twisted sideways on the car. As Christine is in reverse and dragging the Camaro along you can see down through the hood that the engine compartment is empty. Minus a transmission also, I believe. (01:15:30)
Revealing mistake: At the end when Norman is being stabbed at by Mary dressed up as Mother, Mary stabs Norman in the hand. You can plainly tell that this hand is a doll, as it is not a natural colour, it is stiff and is stationary, unlike Norman who is moving his hands. (01:35:10)
Revealing mistake: The shark attacks a little wooden platform in the water which 3 men then fall through. You can see this is made from a lightweight wood such as balsa so that it will break apart easily, and it's not the sort of wood such a thing should be made of.
Revealing mistake: The outline of the blood pack is visible under John's shirt when Stillson's body guard shoots him. (01:37:35)
Revealing mistake: When Tad begs his Mom to try turning on the car, Tad crosses his fingers before his Mom asks him to. (00:51:15)
Revealing mistake: As Mr. Connor flies into the retaining wall after being thrown from the Vietnam setting, you can see the "stone" structure wobble.
Revealing mistake: When the police are called back to camp on the night Megan, Judy and the group of kids are murdered, the mustache on Officer Frank is obviously fake.