Factual error: The equation written on the board does not come out to be "11", in fact, it's not really solvable because it doesn't have 2 sides, just a "?" on one side.
Audio problem: When Josh is telling Ben Stiller that the candy belongs to Seymour Butts, his lips don't match the words he's saying. In the next shot, Ben Stiller responds, and his lips don't match the words he's saying either.
Continuity mistake: The scene of the kids playing on the blob when they first arrive at camp is the same scene towards the end after Pat takes over.
Continuity mistake: After the campers take over the camp, many counselors are tied to trees. When the kids are putting honey on Lars, the left strap of his tank top falls down. In the next shot of Lars crying with the deer, the strap is back upon his shoulder. (01:09:19)
Continuity mistake: After Lars makes the children do a Buddy Check in the lake, the nurse says something like "Well I see that you have a lot of power" and then walks past him. But when the shot zooms out, she is no longer on the screen.
Deliberate mistake: At the end of the movie when Gerry launches the go-kart in the air, all the spectators are about 50 yards away yet they are looking straight up as if the go-kart is flying above their heads.
Audio problem: During the Apache Relay Race, the boy who is swinging down the rope screams. But if you look closely his mouth is not moving at all.
Continuity mistake: The stack of books falls over when Roy breaks into the room. However, when they leave, the same books are stacked perfectly.
Character mistake: In the scene when they do the weigh in, the camera man recording Ben does not even have the tape door pressed into the camera, so nothing is being recorded.
Continuity mistake: The nurse's hair changes color throughout the movie.
Audio problem: When Jerry gets back on the track after the MVP racer runs him off, the MVP racer says "Oh, shoot." His lips, however, say a swear word. (01:30:00)
