Factual error: The movie takes place in 1981, but when the councilors decide to go into town they jump in the back of a very battered looking 1985 Chevrolet pickup.
Continuity mistake: Even though it's supposedly warm enough to go swimming and wear shorts, you can see the actors' breath as they speak. It's very noticeable in the first mess hall scene where Gene is yelling and later when Andy is watching the kid water ski.
Continuity mistake: When Coop tells Katie he's going to cancel the order of onions and limburger cheese, there's a girl with a red and white striped shirt passing by him on his left side. The shot changes to Katie, and when it goes back to Coop, the same girl is passing him but on his right side now. (00:05:50)
Continuity mistake: At the very beginning of the movie, the kids are trying to wake Coop up by singing to him. We see an overhead shot of the kids and the redheaded boy without a shirt on is to the right of the boy with the tennis racket. The shot changes and the red headed boy is now on the left of the kid with the tennis racket. (00:02:40)
Continuity mistake: After Beth finishes talking to the counselors and they all walk away, she yells something at all of them, and Katie can be seen on the left side of the screen, at the bottom of the steps tying her shoe. When the shot changes to JJ and McKinley, you can see Katie in the background, suddenly at the top of the steps.
Continuity mistake: When Andy is standing by the table, Lindsay comes over telling him that she wants to make out, but he's all disgusted because she has BBQ sauce all over her face. For the first few angles of the scene, the BBQ sauce is on the corner of her mouth, and on the side of her face a little. But in one angle, it is ALL over her mouth. Then it comes back to the previous angles and it is back in the corner of her mouth again. (00:49:15)
Continuity mistake: When Coop runs to Katie's cabin and sees her talking to Andy, right before he runs up the steps you can see the cabin door is closed. The shot changes and suddenly the door is wide open. Also when he runs up it's sunny, but when he's talking to her it's raining, then it's sunny when he's running off. (00:57:25)
Other mistake: Victor and Neil leave in the Rally STX van to take the boys to Moose River. Later, when Beth goes into town the license plate number is '566 241' on her Chevy pickup, but when Victor drops Neil and the boys off, we see their Rally STX has the same license plate number '566 241' as well. (00:30:40 - 00:36:40)
Revealing mistake: At the start, when the girls in the bunk are standing in front of the mirror, the first shot of them looks as if the camera is facing the mirror and we're seeing their reflection, but note that neither the buttons on Alexa's blouse nor her white bracelet are on the opposite side. The "mirror" is actually regular glass with the girls standing behind the glass to mimic a reflection, though Alexa's blouse and bracelet reveal the secret. (00:03:05)
Factual error: Nancy is sitting on the porch knitting, however the orange and yellow blanket she is working on is crocheted. These are two very different crafts and crochet items can not be made with knitting needles. (00:30:00)