In the beginning, an old woman is suffocated by a plastic bag by the paperboy. You see her face behind the plastic bag as she dies, and her mouth is wide open. It cuts, and the paperboy removes the plastic from the woman's head. Her mouth is now closed.
The mother drives up to the paper boy's house, and she leaves her door open and runs up and into the house. Then, when she escapes the house, she goes to her car. Now, the car door is closed and the doors are locked. The paper boy could not have closed and locked the car, because he was inside the house the whole time.
Johnny's father is buried in the basement cooler after being killed, but his corpse is later seen buried in the hole that Johnny was digging up earlier.
When Johnny takes a Polaroid of his own face, he doesn't bare teeth when he smiles. After the photograph develops and is added to the collage of his "family", he is showing teeth.
When Johnny uncovers his dead father's head in the freezer, his neck can be seen pulsing.
Mrs. Rosemont is shown several times using an inhaler for her asthma. She holds the inhaler a good distance away from her mouth when using it. The correct way to close your lips around the device as you use it.