Continuity mistake: Near the beginning Buffy tears off her dress and throws it on the ground. When they walk away there's no sign of it.
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.
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.
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.
Continuity mistake: At the end of the Matrix scene he throws Cindy into the wall, look when she hits the wall there is no sign of hitting the wall, but when she is falling to the ground they is an imprint like an oval on the wall.
Continuity mistake: When the six characters are imitating the scene of I Know What You Did Last Summer, they get out of the car after it has spun around. All of the headlights are on, the two yellow and the two white. Later, if you look behind them, the left headlight is off.
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.
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.
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.
Continuity mistake: In the scene where they hit the fisherman, they spin the car. Notice the yellow line, they are somewhat over it in one scene, then in the next the line in to the right of the car, not under it.
Continuity mistake: In the scene after they look at Greg's report card, Ray has his hand on Brenda's ass, in the next angle it is on her shoulder.
Continuity mistake: When Greg stands up through the car's sun-roof, during the flashback, he is holding an empty bottle, but when he is at the top of the car the bottle is nearly full.
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.
Deliberate mistake: When Cindy is talking to the killer on the phone, and he says, "I could be anywhere. I'm like the wind, baby," she walks into the living-room. Notice the wall behind the couch, it is completely different a moment later. When the killer hides behind the curtains, the wall behind the couch has large bay windows with seating underneath. Then when the killer is at her house the second time, all the windows are gone during the Matrix send-up, so Cindy can run along that wall.