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.
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.