Continuity mistake: In class, the teacher tells Sidney "It appears to be your turn." One of her classmates, a girl with a grunge shirt, turns around to look at her, but in the next shot she's looking ahead. (00:18:55)
Continuity mistake: When Tatum asks "Why would they ask you if you like to hunt?" look at the blue backpack. Next shot, and the light is on it in a different position than before. The position of the various actors as they eat grapes also changes. (00:19:50)
Continuity mistake: When all the guys are sat outside of the school talking about who (a male or a female) is the murderer, Tatum's leg is behind Stu's leg. In that same action, we go to a close up and suddenly Tatum's leg is in front of Stu's leg. (00:19:55)
Continuity mistake: The gang is chatting about the murders and their interrogations. Stu responds "There's no way a girl could have killed them" to Tatum's complaint that nobody asked her if she likes to hunt. In these two shots, Rose McGowan's hair is wildly different. (00:20:00)
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: When Tatum calls Sidney at 7:15, she reaches over to get the phone. The sleeve is at her elbow in one camera angle, but it's instantly at her wrist in the shots before and after. (00:25:15)
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)
Revealing mistake: When the killer surprises Sid after she's come in from outside and locked the door, he tries to stab her with his left hand, misses, and hits the door right next to the chain in closeup. In wide shot (very quick shot) when Sid legs it, look at the killer and you can see he's holding a very badly bent knife in his right hand, nowhere near the chain. (00:27:55)
Continuity mistake: After Sidney has been attacked and is in her room. Billy climbs through the open window. It is completely open. After he drops his mobile phone, the window is only half open. (00:28:35)
Continuity mistake: When the killer pops out from the closet after Sidney closed the front door, he's holding the knife above his head, but it cuts then to a shot of him raising the hand from a position below the waist. (00:28:35)
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: When Sidney manages to kick Ghostface away after he has almost stabbed her behind the front door of her house, she sets up the kick shouting "no" and shielding herself with her left arm, but in the shot of the actual kick the stuntwoman's left arm is on the ground. (00:28:55)
Deliberate mistake: When Sidney is typing the message to the police, you can see that there are red lights flashing, which must mean the police are there, 5 seconds after she types. Obviously deliberately done for the humor. (00:29:30 - 00:30:25)
Suggested correction: Contrary to what the entry says, I don't see police lights flashing as she types, nor when she talks to Billy. I do agree that still it's barely a minute before the police arrive in full force on the scene and it's pretty ridiculous (although I am not sure it's deliberate humour).
There's a time skip between Sidney encountering Dewey at the front door and Billy being arrested. It's plausible Tatum had sent Dewey to check on Sidney knowing she was going to be late, and so he arrived before the rest of the authorities. Billy did not chase after Sidney and likely reacted calmly to Dewey to look as innocent as he could, he wouldn't necessarily have been arrested right away.
Continuity mistake: Billy holds Sidney in his arms after the attempt at her life downstairs. She clings to him and pulls at his jacket, that is unperturbed in the close-ups on Skeet Ulrich. (00:29:55)
Visible crew/equipment: When the officers take Billy away from Sidney's house, a set of lights is reflected in the back window of the car. (00:31:00)
Continuity mistake: At the police station, Billy looks back with anger at Sidney after the sheriff tells him that they have to detain him until the phone records come in. The sheriff is looking at him with his arms crossed, but in the close up on Skeet Ulrich the sheriff's got his hands on his thighs. (00:34:10)
Other mistake: Two police officers drag Billy Loomis out from the sheriff office across the station; the younger officer stares into the camera right before it cuts away. (00:34:40)
Continuity mistake: When Tatum comforts Sidney telling her "I'm gonna get you out of here, okay?" in the background her brother comes out of the door holding the 'Father Death' costume box. The sheriff by him is holding an orange paper, but at the cut he's got his hand behind his back, no orange slip. (00:35:00)
Continuity mistake: The costume of Ghostface/Father Death is stuffed inside the plastic bag in two different ways in the shots when Sheriff Burke is checking it out - look at the bits coming out in the close-up. (00:35:05)
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)