Continuity mistake: After Ben stopped his car in front of Carter's house, a front view of the windshield did not show either of the shattered sections from the earlier collision with the deer. Damage was first on the driver's side then on the passenger's side, but now on neither side. (00:15:55)
Continuity mistake: The collision with the deer shattered the windshield in front of driver Ben, but when Ben skidded to a stop, there did not appear to be any damage to the driver's side windshield. When Ben and Carter were getting out of the car and when they were changing the front passenger side tire, the passenger-side windshield was shattered (and closer to the hood compared to midway between the hood and roof on the driver's side, which was no longer there). (00:10:20 - 00:11:04)
Continuity mistake: The way the deer's front legs were crossed and the location of its guts differed before versus after Scout Leader Rogers pulled his pocket knife out of the deer's eye. (00:17:51)
Revealing mistake: From the sound made when the car hit the deer, as well as the deer's overall appearance, it was obvious the deer was fake. The fake deer's body was almost uniformly brown, but the "dead deer" on the road had a white underbody that went part way up its side and along its legs, which should have been visible on the "fake deer." (00:10:19)
Continuity mistake: When the gang meets the zombie that likes Britney Spears, he's got his left arm outstretched trying to grab them. In the next shot, his arm is lowered.
Character mistake: When the 3 boys and Rogers are trying to recruit scouts, they pledge to Rogers and Carter raises his left hand but in the next shot he has his right hand raised. (00:09:05)
Continuity mistake: When the party goers are escaping, Ben begins tying the door closed, but in the next shot, there are still people running up the stairs escaping. (01:19:30)
Deliberate mistake: The snacks in the vending machine were almost to the top of each display shelf, but an interior to exterior view showed the lab researcher's head unobstructed and a foot or so clearance between the snacks and the top of the shelf. (00:06:30)
Other mistake: Scout got bit in the butt but never turned into a zombie.