Continuity mistake: When the killer sneaks up on Randy, Randy is lying back against the sofa. When Ghostface raises the knife Randy is lying back, relaxed with a tired look on his face. On the delayed footage when the killer raises the knife, Randy leans forward and is practically on the edge of the seat, his mouth and eyes wide open. (01:22:55 - 01:23:30)
Continuity mistake: When Tatum goes into the garage before she gets killed,she goes to get beer. She then walks over to the garage door opener with the beer in her right hand. Her left hand is reaching up to push the button, but as they show the close up, it is her right hand pushing the button. (01:05:35)
Continuity mistake: After her first time with Billy, Sid brushes her hair. She puts the brush back on the bedstand, but the phone on it changes angle between shots. Later in the scene, you can also see the brush's handle sticking out from the side of the bedstand by the bed, or the one facing front. (01:18:55)
Continuity mistake: When the whole gang is watching Halloween, they see the scene in which Michael Myers impales a victim with a knife, which suspends him from the wall. Just before Randy pauses the movie, Michael Myers is standing and admiring his handiwork. When Randy pauses it, the frame is of Michael Myers raising the knife, which of course, happened 10-15 seconds ago.
Continuity mistake: When Randy explains the "Rules" to everyone and mentions the rule of no sex only two guys throw popcorn at him. Also they only throw one piece at a time, yet when Randy says "Big nono, big nono" you can see bucket loads of popcorn flying at him. (01:13:20)
Continuity mistake: When Randy is explaining the rules of a horror movie to the people at the party he pauses the movie and says "Jesus Christ you don't know the rules?" When the camera guy is in his van later we hear this audio again on the recorder but instead Randy just says "You don't know the rules." (01:13:00 - 01:14:00)
Continuity mistake: When Casey puts the two videos on top of the TV, she puts them on top of each other so they are placed neatly. Then when she picks up the letter opener off the TV later, the videos are no longer stacked neatly. (00:08:10)
Continuity mistake: At the party at Stu's house, when Dep. Dewey is walking through the house looking for the killer, Dewey walks into the living room with the TV and couch. Look at the TV, there is a white phone sitting right next to it. Later, when Sydney and Stu are fighting and she is about to push the TV on top of him, the white phone is gone. The TV also appears to be bigger. (01:40:40)