Continuity mistake: When Greg confronts Ray about the picture he found in the locker room, he shows them all and they start laughing. Buffy is on the left part of the screen, (on Cindy's right side), then Cindy explains that she got a note. Then when she says: "Somebody knows.", Buffy is more to the right (or left of the screen) than before. Then when Cindy says they have to call the police, Buffy's back to where she was at first. (00:26:50)
Deliberate mistake: When Greg gets murdered and Cindy, Bobby, and Buffy are trying to figure out what happened, you can see the killer is mopping up the blood. However the floor is carpeted so the blood wouldn't clean up, it would smear instead. (00:31:20)
Revealing mistake: When Cindy is in the bath and she starts to shave her face, she repeatedly shaves the long head hair which has fallen over her face, and yet it is obvious none of it comes away with the razor, indicating there isn't a blade in it at all. (00:32:15)
Continuity mistake: In the scene where the killer is in Cindy's house, the killer is hiding behind the couch. When you see shots of the killer, the cell phone is in his right hand and the hook is in his left. When she notices him and he stands up, the phone is in his left hand and the hook is in his right. (00:33:30)
Continuity mistake: When Cindy is running up the stairs and throwing the bicycle and piano at the killer the staircase is straight but when she goes to open the door and sees Doofy, if you look behind her the stairs are spiral. (00:34:30)
Continuity mistake: In the scene where Buffy and Cindy get dressed in the locker room, a girl standing right next to Buffy first drops her towel to get dressed and a few seconds later has the towel wrapped around again. (00:44:05)
Visible crew/equipment: When the teens are all standing out side and the teacher is ready to jump from the school building. As he is jumping you can see the shadow of the scaffold he jumped from in the left bottom hand corner of the screen. (00:48:20)
Revealing mistake: When the teacher jumps it's clear the ground is a mattress with grass and leaves over it. Soil would not bend the amount it does, even with someone jumping off the roof of a building. (00:48:20)
Continuity mistake: When Ray is with Brenda in bed, and she get out, we can see her pillow in one form, and in the next scene is in another form. (00:49:20)
Continuity mistake: When Ray tells Brenda to put on his football gear, he hands Brenda his shoulder pads. When Brenda accepts these she has two braids hanging down in front of her. The camera cuts to Ray for a second then back to Brenda. When the camera has cut back the two braids have moved over her shoulder. She couldn't have moved them with her hands as she is holding Ray's shoulder pads with both hands. (00:49:30)
Continuity mistake: In the scene when Ray goes to the restroom while at the theater there are men urine racing.There are five urinals. The man with the white hat is to left. The man with a black cap is to the far right.when the third man from the left is declared winner.The man with the white hat shifts right one space and the man with the black hat takes his old spot. (00:55:45)
Revealing mistake: When the man in a striped shirt stabs Brenda at the movie theatre, he pulls the knife out and there is no blood on it. (00:56:05)
Audio problem: When Brenda is in the movie theater, people are hurting her and yelling at her, but no one's mouth moves. (00:56:30)
Continuity mistake: In the scene where there's a party at Cindy's house, two kids behind her are drinking liquor out of bottles that are completely upside-down, but the level of liquid remains constant. (00:57:00)
Continuity mistake: Just after Brenda drops the first beer bottle, her hands are out in the "don't shoot" position. The camera cuts and she is holding the bottle in both hands. (00:57:50)
Revealing mistake: During the final party scene, where Cindy is wearing a Viking Hat and yells with joy as she drinks from a "Beer Bong", if you look closely, right before they pan to Cindy, you can see that the hose of the "Beer Bong" is not attached to the funnel, or anything for that matter...it is just held alongside it. (00:58:40)
Continuity mistake: In the scene in the bedroom between Cindy and Bobby, just before he explains about sucking on a tootsie pop, Cindy's hair is all messed up. Camera cuts and it is fairly different. (01:02:15)
Continuity mistake: Near the end of the movie, when Ray is stabbing Bobby, Cindy says "You've watched one too many TV shows." Ray points the knife at her. At this point the knife is in his left hand but when he turns back round to stab Bobby again the knife is back in his right hand. There is not enough time for him to swap hands between shots. (01:10:25)
Continuity mistake: When the killer jumps up behind Ray and stabs him through the back with the hook, we see he obviously gets lots of blood on it. Watch it when he goes to stab Cindy and misses. It hits the cupboard and is completely clean. The hook is clean for the rest of the time he has it. (01:10:50)
Continuity mistake: In the scene where Ray is killed, the killer stabs Ray with his hook. Ray's shirt is not bloody, but as he falls it is. Then when he lands on top of Bobby his shirt once more is clean. (01:10:50)
Chosen answer: I know for sure they were making fun of the movie 'Usual Suspects' (dropping the cup) - they might have added the gag of the fish in it to appear as though she was shocked by the fish instead of the true identity of Doofy.