Revealing mistake: In the Kentucky church-massacre scene, Harry briefly scuffles with a man in a light blue sweater. Harry elbows him in the ribs, sticks a grenade in the man's pocket, spins him around and delivers a crushing blow to his neck, then hurls him head-first into a wall. Throughout this sequence, the man is obviously a live human being. However, a fraction of a second before he impacts the wall, he transforms into a life-size rubber dummy before our eyes, in mid-frame, without any obvious camera cut. This demonstrates the complexity of the scene - it is a digitally-edited collage of action sequences almost seamlessly strung together into what appears to be one long traveling shot.Charles Austin Miller
Revealing mistake: As Glenn, Blake and Monica are being surrounded by zombies, as Monica asks "Fucking hell, how many more of these are there?", in the background you can see a zombie sitting astride his victim, flailing away with a hammer or hatchet. It is obvious that he is just swinging his arm back and forth, without connecting with anything. It looks as if he is dusting, not slaying someone. (01:23:50)Twotall
Revealing mistake: About seven minutes in, during the scene where we see Cooper helping the Nerd as a cameraman, you can tell that Cooper has been added to the scene using green-screen effects, as the actor was unavailable to shoot at the location. The lighting on Cooper doesn't quite match the lighting of the scene, and you can see a slight "blur/feathering effect" around him where the greenscreen background was removed.
Revealing mistake: When Felix talks breaking the fourth wall about the mysterious, vicious "Roxy", he shows her twitter page. The latest tweet is dated Mar 10. Since the school at that moment still has to issue the report cards for the first semester, it seems a little too far ahead in time. (00:08:40)Sammo