When Casey is making popcorn, she puts the salt shaker next to the stove, and leaves the kitchen. When she comes back the shaker isn’t there.
When Casey is making the popcorn, she starts pulling the cover off with her left hand near the handle. In the next shot she is seen using her right hand pulling the paper cover from the other side.
When Casey sees Steve on the patio, the killer tells her to turn off the light. You see the shadow fall across his face. Yet when the camera flashes to Steve just before he’s killed, we see the already turned-off light go off again.
SPOILER: When the killer is chasing Casey outside her house, the part of the mask that hides his neck is grey. But when the killer is strangling Casey on the grass, the neck part is jet-black and the face of the mask is also wider.
After Casey is stabbed the first time she knocks the knife out of the killer’s hands, causing him to start strangling her with both hands. When she fights him off, the knife is suddenly back in his hand again.
When Sidney looks out from her window and says, “Well I call your bluff.” She then opens the door, and apparently opens the door to where it’s facing towards the outside. But when she steps out, the door is facing inwards, into the house.
Sidney’s police jacket at police station.
No open handicap stall when Sidney enters school bathroom.
When Sidney is at the school bathroom sink her bracelet continually moves from one wrist to the other in between cuts.
The amount of paper on the floor, around the trash can, in the school bathroom.
The placement of hanging clothes in the principal’s closet.
When the principal goes to open the door the first time. The door opens left to right (the hinges are on the right side.) When he closes it he closes it left to right (the hinges are on the left side).
Length of the sheriff’s cigarette during the conversation with the deputy.
When Dewey walks into the party, he takes a beer bottle from a teenager, he then gives it back but in the next shot he still has it.
SPOILER: When Gale and Dewey go in to the party, Gale secretly places a video camera on top of the VCR facing the couch. The camera is placed at waist-level directly behind her. However, the height of both devices change. When Randy picks up the phone to receive the news of Principal Himbry’s death, he is standing upright and the camera is directly in front of his mouth.
When Tatum is getting beers from the refrigerator in the garage, she is seen grabbing beers and holding them in her right arm. When she’s done, she is originally seen from behind holding a beer in her left hand, and closing the door with her forearm, but then it switches shots, and her left and is holding two beers with her hand tucked into her arm, and closing the refrigerator door with her foot.
When Tatum throws the beer bottles at the killer in the garage, they break and wet his costume, but when the killer runs and falls over her, his costume is suddenly dry.
When Tatum is locked in the garage she reaches up to hit the garage door button to get out with her left hand because the beer bottles are in her right. On the close-up of her hand pushing the button it’s her right that hits it.
SPOILER: The amount of blood on the knife in garage after cutting Tatum.
At Stu’s party, everyone watches Halloween (1978). However, the scenes shown from that movie do not correlate with the time passing in this movie. For example, the time between Laurie finding her friends murdered and the “closet scene” is ten to twelve minutes in Halloween; in this movie, closer to 30 minutes elapse.
Randy says “Here comes the obligatory tit shot” while watching Halloween (1978) and everyone cheers, supposedly at the sight of breasts, but the scene they are watching at that precise moment doesn’t show nudity. The girl’s breasts in Halloween aren’t revealed until a later scene (and, some claim, not at all in the video version).
The number of standing beers on table during the “rules” speech.
When Randy and friends are watching horror movies, Randy says, “She always outsmarted the killer during the big chase seen. Virgins always do that.” However, when Kenny and Gale watch the footage on their hidden camera, the sentences have been shortened to, “The virgin always outsmarts the killer in the big chase scene.”
The white car disappears when running Dewey and Gale off the road.
SPOILER: When Tatum dies her head is seen being squished completely but later when Sidney finds her body, her head is still there and her neck is being squished.
SPOILER: When Tatum is killed in the garage, both of her arms hang in mid air, but when Sidney finds her dead, only one of her arms his hanging down.
SPOILER: The bloodstain after Billy gets stabbed.
SPOILER: In the end, there are no cuts or stab marks on Stu after Billy stabs him many times.
SPOILER: When Stu is setting up Sidney’s dad to be framed, you can see him put the cell phone in front of the voice changer box in his pocket. But when it cuts back and her dad is pushed to the floor, you see the cell phone is now behind the voice changer box.