Revealing mistake: During the scene when Cindy and the killer are fighting Matrix-style, Cindy kicks the killer, and he knocks down the book case so it falls over him. There is a vase with flowers on the book case - when it falls down the vase still remains on the book case, glued to it. (01:11:30)
Revealing mistake: During the final party scene, where Cindy is wearing a Viking Hat and yells with joy as she drinks from a "Beer Bong", if you look closely, right before they pan to Cindy, you can see that the hose of the "Beer Bong" is not attached to the funnel, or anything for that matter...it is just held alongside it. (00:58:40)
Revealing mistake: In the snatch and run scene right at the end of the film, when the store owner gets his gun, you can see he doesn't fire it, there are just sound effects. You can easily notice this because the owner's hand doesn't move when he "fires".
Revealing mistake: At the very start of the film when Cindy hears a noise outside her window and goes to check, she was on her computer. But if you look closely when she stands up you can see that the computer isn't even switched on. (00:04:35)
Revealing mistake: When the killer is getting kicked into the glass cabinet you can see a string pulling the glass so it will break. (01:14:25)
Revealing mistake: At the end in the "Matrix" fight scene, the killer throws Cindy against the wall, which moves at the top. Watch the gap at the top of the wall. (01:11:00)