Continuity mistake: At the very end, when Sid finds out who the killers are, they are all standing in the kitchen. When Billy and Stu stab each other take a look at the blood stain on the left side of Stu's jumper. It starts around his shoulder and vertically goes down towards his waist. When Sid is fighting him in the lounge she gets up and goes behind the TV. In the shot looking straight down on Stu from a birds eye view, notice the blood stain is now horizontally across his stomach. You'll have to look closely for this one.
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.
Audio problem: At the party, Gale places a portable small camera on top of the TV to spy on the teens there. Later, the teens are watching the Halloween movie on this very TV and talking loudly. The movie is playing with sound when they are watching it. However, when we see Gale and Kenny's perspective as they are watching the feedback, they can hear the teens talking. However, despite the camera sitting right on top of the TV, it doesn't pick up the audio from the movie playingr. This mistake is repeated not long after when Ghostface is sneaking up behind the one teen left behind on the couch who's watching the movie at an even louder volume.
Continuity mistake: When Skeet is first shot by Gale he crawls backward, but if you look at the ghost face behind him there is no knife there. The next shot there is a knife on top of the ghost face.
Continuity mistake: After the killer calls Casey the second time she puts a salt shaker on the counter, she walks round to her living room, and the killer phones her two more times. When she gets back to the kitchen the salt shaker has disappeared.
Character mistake: Sid deduces that Billy could be the killer because he could have used his phone call from jail to make the threatening call. However, the deduction has to be incorrect, since if it was really Billy, he could have never used the voice-changing device.
Suggested correction: This will sound pedantic (hey, it's MovieMistakes.com, we're entitled), but I don't think this is what is meant by a character mistake. Sidney isn't presenting an erroneous fact that goes uncorrected, she's explaining an idea that had crossed her mind. Billy immediately gives a plausible response and by the end of the film it's evident who'd called her. The takeaway isn't that Billy could still be the killer but that Sidney can't help but suspect him despite their reconciliation.
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 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 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.
Other mistake: During Tatum's murder we see some problems exacerbate. The killers are not supposed to be invulnerable and are wearing a cheap costume, but they receive hard hits (Tatum breaks two bottles of beer, one straight to the face) and they don't have a single scratch. When she is killed, nobody hears her scream and nobody else needed to grab a beer either. Furthermore, Ghostface has the garage door fully open, but without knowing who is on the other side, that is one room away from the others, goes by the mysteriously unlocked door to the inside of the house. And we see Billy (who should be the killer there, since Stu was at the party) join in coming from outside.
Factual error: Throughout the movie there is constant reference to the Sheriff; Burke is the sheriff, Dewey works for the sheriff (and he will become the sheriff in Scream 4, with the same mistake happening), but the car Dewey uses is marked "Woodsboro Police."
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.
Factual error: At one point when the partygoers are watching Halloween, Randy alerts them about the "obligatory tit shot" and afterwards the viewers react with great satisfaction, however, in the referenced scene in Halloween, the naked breasts are actually kept out of frame.
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.
Other mistake: When Stu brings Sidney's dad out in the kitchen, you can see behind him a September 1996 calendar. Earlier in the movie, the scenes inside Principal Arthur Himbry's office do show a September calendar, which is obviously the intent of the movie, but it's a September 1997 calendar.
Continuity mistake: Sidney is on the roof trying to escape from the killer and she falls off. When she gets up she sees the dead body of Tatum in the cat door and her left arm must be behind her because you can't see it but this isn't what happened when you saw her die. Her left arm was inside the garage and was beside her. Unless if fell off, it should be next to her body.
Continuity mistake: When the cameraman is watching the 30 second delay footage and the ghost face is about to kill Randy who is on the sofa, he walks into the room in a different way on the delayed footage to on the actual film footage.
Character mistake: When they are surprised by Gale, Billy angrily says to Stu "Man, I thought she was dead." To which Stu replies "She looked dead, man. Still does." However, Stu didn't have time to check on Gale, since she crashed the vehicle moments before Sidney is attacked by a Ghostface that had to be Stu himself (since he does the quick clothes switch coming from the car).
