Unlike most zombie films, aside from the sound of sirens in a very early scene, there are no police officers or military soldiers present or seen at anytime in the film.
At the start of movie, the "tryouts" sign board put in front of judges tables changes its position from the corner table to the center one, all by itself.
While she's killing zombies at the funeral home there is a lot of blood splatter on Gwen's face, then when in the back of the hearse there is no blood on Gwen's face. The blood is back on her face when she arrives at the coach garage.
When they discover the girls hiding in the bathroom, we see George removing his football helmet. However, in the following over-his-shoulder shot, we can clearly see he still has the helmet on.
The speed of a zombie in this movie is determined by the amount of time he or she has been deceased. The zombies that were buried recently can launch out of graves and run like cheetahs. The ones that were buried long ago define your stereotypical zombie that drags his heels as the heroes get away.