Continuity mistake: During the whole bathroom scene the trash bin by the exit door is oriented parallel to the wall or perpendicular. The mistake can already be spotted early in the scene when the cheerleader is berating Sidney, but it is much easier to notice it at the very end not just because there are multiple consecutive shots from different angles, but also because to make possible for Sid to collide with the bin as she slides across the floor, the bin has been placed almost two feet away from the wall. (00:46:30)
Continuity mistake: Tatum is growing impatient while Sidney is sitting in the police station waiting to be released, and she hurries her brother. In this sequence there is a blatant lack of continuity whenever the editing switches to reverse shots, as Rose McGowan's hand and Neve Campbell's movements don't match between angles. (00:35:25)
Continuity mistake: Sidney is rather inexplicably covered in blood when she reappears to stop Gale from driving off in the news van without her (even her hair is drenched!). It's true she'd been off-screen for a while and who knows what's happened to her, but it's hard to come up with an explanation from what we've seen, especially since the implication is that she's simply been hiding out in the fields this whole time.
Continuity mistake: When Sidney and Billy are talking in the bedroom at Stu's house, when the camera is on Billy, Sidney's hair is in a different position than when the camera is on her. (01:20:00)
Continuity mistake: At the end when Sidney is in Dewey's police car and the killer is there, she opens the door and falls out but the door is still locked. In some cars you can open the door when it is locked but the lock always pops up after you open the door, and this one didn't.
Continuity mistake: When Randy answers the phone he kneels down putting his head about level with the top of the TV, yet when Sidney goes to drop the TV on Stu's head the TV is much higher.
Continuity mistake: After Courtney Cox runs to the van when she's being chased, she hops into the van and throws it into reverse, guns it, then slams on the brakes, and the body falls down onto the windshield. Slamming on the brakes after going in reverse would cause the body to fall the other way, toward the back of the van. (01:22:50)