Continuity mistake: At the lake when they pull the floating object by the pier the girl on the right side is about ten feet ahead of the object. When it cuts she is behind it. (00:21:35)
Continuity mistake: When the kids are at the beach, Brenda shows up saying "Hey you guys. Ready to get back to work?", while placing her foot on a red towel. When it cuts the towel has changed position. (00:23:00)
Continuity mistake: Brenda is seen swimming really far out to rescue Ned, and Marcie rows her boat out to the middle of the lake, yet when they rescue Ned, they are right beside the white decking. (00:23:15)
Revealing mistake: When Ned is pretending to drown, Brenda swims out to rescue him. You can see that she and Ned stay underwater for a few seconds, until their cue to emerge. (00:23:30)
Continuity mistake: When they see the snake in the cabin they all jumps after it under the bed in panic. But in the next shot from under the bed you see them calmly lifting the sheet on the bed to look under it. (00:25:25)
Continuity mistake: First Bill and Alice are looking under the bed for the snake. In the next shot Alice is not the one looking under the bed, but she is kneeling behind Marcie, who now is looking under the bed with Bill. (00:25:35)
Visible crew/equipment: After they've killed the snake, Alice says "Is it dead?" and as the camera pans up, the boom mic's shadow is visible moving across the wall, directly over Ned's head and the red box. (00:26:05)
Visible crew/equipment: When Officer Dorf gets on his bike and says, "You kids keep your noses clean you understand? You'll be hearing from me if you don't", the reflection of the camera man walking can be seen on the side of the bike. (00:28:05)
Audio problem: When the kid is playing classic guitar the movement on the guitar's neck doesn't match the music. He somehow manage to play high tones on low frets. (00:36:45)
Deliberate mistake: When they are playing strip monopoly, Alice purchases Baltic Avenue and then Bill rolls the dice and Alice exclaims that he's rolled an "8" - putting him on Baltic Avenue. However if you look carefully at the dice (before Brenda quickly scoops them up) you can see they show two 5's. (00:40:05)
Revealing mistake: When Jack is stabbed through the neck, it is blatantly obvious that the neck is fake. You can clearly see the line between the real and fake neck. (00:41:45)
Visible crew/equipment: In the scene at the diner after the kids have played "Strip Monopoly" there is a shot of Sandy behind the counter and some customers walking out of the diner. Look behind the last woman walking out and you can see a crew member reflected in the window. (00:46:25)
Visible crew/equipment: At the diner, when Sandy walks to the other end of the counter and talks to Steve, the reflection of the boom mic is visible at the top of the window behind Steve. (00:48:10)
Continuity mistake: When Steve's car won't start you see a police car pull over. The sheriff turns on its red lights and Steve goes towards it and opens the door. In the next shot you see him talking to the sheriff, but now the lights are off, it cuts again and the lights are on. (00:50:30)
Continuity mistake: After Brenda hears a noise, she puts her book down next to the candle, and walks to the door. When she gets to the door, the book is now by the opposite side of the candle. (00:52:50)
Continuity mistake: After the sheriff gets the call over his radio, he turns on his red lights. In the next shot they are off again, and are then turned on once again. (01:00:25)
Continuity mistake: When Alice wakes up she has white socks on. When she walks to the kitchen they are black. (01:08:00)
Revealing mistake: When Alice finds Bill killed and hung up on the door you can see Bill blink his eye. (01:08:05)
Continuity mistake: After Brenda is thrown through the window, she is facing to her right. Later when Alice goes back to the kitchen, she is facing to her left. The glass and wood around her changes too. (01:11:20 - 01:20:15)
Revealing mistake: When Brenda's body is thrown through the window, the movement of her head when hitting the floor is not "limp". She positions her head for the landing, then deliberately tilts it to the side as if dead. Also, on the second cut from Alice to Brenda we can see Brenda's head moving ever so slightly. (01:14:17)
Chosen answer: Just after the credits, there's a bank sign that says "Friday, 13 - 7:01 - 60 Degrees". Then the DJ says "It's 7:01 on Friday the 13th of June." and goes on to say some more about it and lists some other bad luck superstitions. At two other points in the movie, two characters (Ralph and Tierney) say "it's Friday the 13th". So there are at least four references to the fact that the movie takes place on Friday the 13th.
Myridon