When Bibi removes her bra, shot before they were kissing each other, but now her date is farther away so a shot of her breasts can be made.
When Shirley asks Rick for second time does he want his treat, her hair is different in two following shots.
Shape of the cross formed by a hole changes throughout the shots at the end of the movie.
In a scene involving the preparation of a Halloween party, a student can be seen briefly stacking cans of Coca-Cola onto a table. The Coca-Cola cans feature the Sundblom Santa Clause which is an annual Christmas marketing campaign by Coca-Cola just before Christmas and not as early as October (when the party takes place). This may possibly indicate this portion of the film was filmed around December or just after.
Demonic Rick tells Father Bob that he broke the 5th Commandment "Thou shall not kill", but it is actually the 6th Commandment that says "You shall not murder. The 5th Commandment is "Honor thy father and thy mother."
When Kurt is decapitated by Angela, his body moves around side-to-side with his hands up in the air near his decapitated wound. In reality, this wouldn't really be likely to happen because the body cannot move without the brain support.
There is a scene where Johnny meets Bibi after he was told to go wake up father Bob and asks her if she's alright even though he just saw her. Then he is finally seen going to wake up father Bob.
When Rick's hand is being crushed, his words don't match the actor's mouth movements.
When the demons speak, their scary voices don't match the actors' mouth movements.