Continuity mistake: Sidney's right hand is in a different position in the two shots that happen when Tatum's mother tells her that there's someone at the phone for her. (00:37:30)
Continuity mistake: Inside Tatum's bedroom, Dewey tosses Sidney an ice pack for her sore hand. Look at Rose McGowan's left hand; she's holding the plush bunny in a different spot between shots. (00:37:00)
Continuity mistake: When Sidney punches Gale in the face, she flies back against her cameraman that catches her putting his hand on her side under the armpit. In the next shot Kenny's hand is on the upper arm, and Gale is also already holding her cheek. (00:36:35)
Continuity mistake: When Gale Weathers 'interviews' Sidney in the back alley, the microphone is turned at different angles between shots. (00:36:30)
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: In the scene where Tatum gets closed in the garage door, the first time it shows her arm hanging down. In the next scene, it shows her arm caught in the door. (01:07:30 - 01:22:15)
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 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: The first time that Casey Becker is stabbed by the ghostface, you can see the knife go into her chest, very deeply, but no blood is there, but directly in the next shot, her shirt is covered in blood. (00:10:50)
Continuity mistake: When Stu puts the voice box and phone in Sidney's dad's jacket pocket and lets him fall, when he hits the ground the voice box partly falls out, but then when they show the dad again the voice box is tucked back in.
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)
Suggested correction: To be fair, we don't see (at least in the DVD version I am looking at?) the VHS boxes for the entirety of the time her hand is on it, and she does bump against the TV set at least twice while talking to the killer, once with the top of the set entirely off-camera.
I would say it's a valid mistake because we do see a shot of the tapes later, and they're still neatly placed (for example, when she says her boyfriend will be there any second), so we know she didn't do anything to them when her hand was off camera. And I never saw any bump hard enough after her boyfriend is killed that would move the top case into the new position it's in.
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: 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)
Continuity mistake: At the beginning of the movie as Ghostface chases Drew Barrymore the killer is wearing a different style of mask and even has a shiny silver material rather than black. As the killer then sits on top of her then choking her, it is the more recognisable mask.
Continuity mistake: When Billy jumps on Sidney in the corridor making his comeback, a bag of potato chips that was lying against the bench's armrest goes from vertical to horizontal. It wouldn't be surprising that a small and possibly mostly empty bag would be toppled over considering the movement that just occurred, however when Sidney headshots Zombie Billy the bag is back being vertical. (01:41:20 - 01:42:30)
Continuity mistake: In the close-up with Sid smashing the vase on Stu's head, her arm is bloodied all the way down to the elbow, while when she reached for the object the blood reached just about the wristwatch. (01:40:40)
Continuity mistake: When Sidney bites Stu's hand, in close-up the wrist is well visible and displays the bracelet in full, but in the wider angle that section is entirely covered by the bloody sleeve. (01:40:35)
Continuity mistake: Stu is slumping against the desk and says he's dying. In the closer angles you can see his left fingers are coated in blood, but in wider angles (for instance when Billy grabs the receiver off him and yells "I'm gonna rip you up, you b**ch"), the fingers are cleaner. (01:38:40)
