Visible crew/equipment: After they've killed the snake, Alice says "Is it dead?" and as the camera pans up, the boom mic's shadow is visible moving across the wall, directly over Ned's head and the red box. (00:26:05)
Revealing mistake: When Jack is stabbed through the neck, it is blatantly obvious that the neck is fake. You can clearly see the line between the real and fake neck. (00:41:45)
Continuity mistake: When Enos is about to give Annie a lift he says "Ok kid, let's move", we see the red clothing going over her shoulder covering her bag's strap. When it cuts the strap is visible. (00:08:10)
Deliberate mistake: When they are playing strip monopoly, Alice purchases Baltic Avenue and then Bill rolls the dice and Alice exclaims that he's rolled an "8" - putting him on Baltic Avenue. However if you look carefully at the dice (before Brenda quickly scoops them up) you can see they show two 5's. (00:40:05)
Continuity mistake: Alice knocks the machete out of Mrs. Voorhees' hand, and we see it land. But when Alice runs and picks it up, it is in an entirely different place. (01:23:40)
Continuity mistake: As Annie backs into the tree, and then has her neck slit, her hair changes styles between shots, and the amount of leaves in her hair changes as well. (00:21:15)
Continuity mistake: When Ned is aiming the bow at the girl the angle of the bow changes between the shots. (00:18:00)
Continuity mistake: While Annie is talking to the woman in the bar the guy that washes the floors (that appeared earlier standing on the other side of the counter) now stands behind the counter by the woman. When Annie is leaving the guy stands on his original position. (00:07:55)
Continuity mistake: When Annie is hitchhiking and the red truck pulls over she is standing in the shade. When it cuts she is standing in the sun. (00:18:30)
Continuity mistake: When Steve is talking to Alice, and begging her to stay another week, he puts his hand up onto the roof as he talks. In the next shot his arm is down. (00:15:30)
Audio problem: Annie walks over to a dog and says "Hi girl! Excuse me, hi boy!" Her lips don't move correctly to the line "..Excuse me.." (00:07:00)
Factual error: After your head is cut off, you wouldn't be able to hold your hands in the air and make fists because your brain controls your ability to do this.
Suggested correction: Not really. There's such a thing as a death twitch. The a chicken's brain controls the ability to run, jump, and flap its wings, but it does just that after its head is cut off. A person could involuntarily clench their fists repeatedly when they've been decapitated.
You're comparing two different animals. The chicken with its head cut off that is still running around is still controlled by the brain. Part of a chicken's brain rests in the neck and when beheaded, it's possible not all of the brain is severed. This is not what happens to a beheaded human. There is a difference between a cadaveric spasm and clenching and unclenching your raised hands.
Continuity mistake: After Alice hits Mrs. Voorhees with a frying pan, Mrs. Voorhees's arm goes from being by her head, to laying across her stomach. (01:22:30)
Continuity mistake: Just one shot before Mrs. Voorhees's decapitation, you can for a split second tell Alice's hands are empty as she swings, and that she's not really holding the machete. (01:24:35)
Visible crew/equipment: When Annie goes into the shop to ask where Camp Crystal Lake is, you can clearly see the reflection of a boom mic in the window, above the head of the cleaner. (00:07:40)
Visible crew/equipment: When Officer Dorf gets on his bike and says, "You kids keep your noses clean you understand? You'll be hearing from me if you don't", the reflection of the camera man walking can be seen on the side of the bike. (00:28:05)
Revealing mistake: When the generator gets shut off they grab a couple of oil lanterns. However once lit you can see they are light bulbs.
Revealing mistake: When Brenda's body is thrown through the window, the movement of her head when hitting the floor is not "limp". She positions her head for the landing, then deliberately tilts it to the side as if dead. Also, on the second cut from Alice to Brenda we can see Brenda's head moving ever so slightly. (01:14:17)
Revealing mistake: After the girl escapes the moving truck, and stumbles through the woods, the killer catches up to her, and slashes her neck. It's obvious she's wearing a prosthetic, as it does not match her skin tone.
Revealing mistake: When Alice opens the pantry door to find Crazy Ralph inside, she is looking directly at the camera as if looking at him, but a second later she's looking to her left.