Revealing mistake: When Sidney in Ghostface costume stabs Billy with the umbrella, you can see the squared shape of a protection pad under Skeet Ulrich's shirt (which she misses the second time around, famously prompting a genuine scream of pain from the actor). (01:39:55)
Visible crew/equipment: When Casey agrees to play the killer's game she crouches down next to the television and as the killer says "Here's how we play..." you can see a clear shadow of the head of the boom microphone cast on the white wooden railing at the top right of the screen. (00:06:25)
Continuity mistake: When Casey is making popcorn, firstly the top of the popcorn that she tears off and places next to the stove changes from being folded in half, to later on laying down flat. Secondly Casey picks up a salt shaker and places it by the stove, but this later disappears. (00:01:25 - 00:03:30)
Visible crew/equipment: Look closely (you may need widescreen to see it) at the railing when Sidney is walking up the stairs outside in her parent's wooden patio talking to Tatum on the phone. You'll notice a quick boom shadow on the right of the camera as it's backing up. [Noticed also by Wes Craven on the DVD commentary track]. (00:22:25)
Continuity mistake: The Halloween scenes in the movie don't match up. For example, Randy is watching the part where JLC first discovers the bodies. About ten movie minutes later in Halloween, she's hiding from Michael Myers in the closet. Then Billy gets the idea to search for Sidney, because that's the scene currently playing. Too much time occurs between scenes for this to occur.
Continuity mistake: At the beginning of the film, Casey is cooking popcorn on the stove. When she peels the top off, you see her peel the side away from the handle, and she's using her left hand, but when the shot changes, she's using her right hand, and is pulling from the other side. (00:01:15)
Visible crew/equipment: There is camera equipment reflected in the door window when leaving the police station. (00:36:10)
Factual error: During the scene where the group of friends is watching Halloween, one boy says something like "Why do they do that? The blood is all wrong. It's too red." The problem is, during that part of the movie, no blood is shown or even implied. Bob is just pinned against the wall. (01:12:25)
Continuity mistake: When Sidney is in the bathroom at school, the trash on the floor around the trashcan changes. (00:45:25)
Continuity mistake: In the garage, Tatum slams the fridge door into the killers face, the killer knocks the door with his arm, and it opens fully. But in the next wide shot of the killer getting up, the fridge door is closed. (01:03:55)
Suggested correction: It happens 01:06:42-43 and Tatum's hand is hovering in the background, she closes it off-frame slightly.
Revealing mistake: When Sidney sticks her finger in the wound made when Sidney stabbed Billy with the umbrella, Skeet Ulriches skin pad visibly does not connect with his neck. (01:41:30)
Continuity mistake: When the killer and Sidney are fighting by the front door, the killer takes the knife and is ready to stab Sidney. Then Sidney kicks him, and he goes flying, then watch as it goes to a wide. He is now much higher in the air than he was a moment ago. (00:27:50)
Continuity mistake: When Sidney and Tatum arrive at Stu's party, they are dropped off by Dewey. Then the two girls walk to Stu's house. The bags Tatum is carrying are switched when they are walking inside the house (when she says "Catering is here"). (01:01:30)
Revealing mistake: After Billy's stabbing, Stu charges Sidney projecting her through a doorway. In that shot you can easily see that Matthew Lillard is replaced by a stuntman. (01:40:15)
Other mistake: In the first scene with Randy telling Jamie Lee Curtis to turn around, the reflection in the TV never mirrors the actual position of Jamie Kennedy. (01:22:30)
Audio problem: Gale exits the TV truck telling her cameraman "I'll be right back" to go with the theme of the movie. However, the line is dubbed over and Courteney Cox says something shorter and different. (01:14:25)
Continuity mistake: When Dewey and Gale enter the house party Dewey jokingly takes a bottle of beer off a party goer then gives him it back. The bottle is back in Dewey's hand again when he speaks to Tatum. (01:03:40)
Revealing mistake: When Sidney is attacked by the killer for the first time (in her house), she is knocked to the floor and you can see she is played by a stunt double. (00:28:39)
Continuity mistake: After Casey has been stabbed in the chest she falls down and the killer gets on top of her, before he can stab her again she knocks the knife out of his hand and the killer instead starts to strangle her. She then kicks him off her but you can see he still has the knife in one of his hands as he falls backwards. (00:11:00)
Continuity mistake: In the final scene where Sidney gives the "coup de grace" to Billy shooting him in the head after he suddenly woke up, he holds the left arm above the mask on his top left, but when he dies, his arm is lowered and the knife appears from nowhere. (01:42:30)
