When Dennis Van Welker is walking the officers car through the car wash, he is wearing khakis when he starts, but jeans when he gets out.
When Zack is making the necklace with that one girl, the other girl comes in and stands behind him. Her sleeve is pulled over her right hand and not the left, yet when the screen switches to another shot, her sleeves are reversed, covering her left hand instead
Morris says the kids are watching Beavis and Butthead which only airs on cable channel MTV, but in a later scene the kids are complaining that they don't get cable television.
Zack's hands switch from inside his pockets, to outside, then back again while he is standing on the rock yelling for everyone to shut up.
When Mud and Gaby are in the bus, they are talking about growing up and dating. In the front shots Mud is laying back in his bean bag, but in the reverse angle shots, he is sitting upright on the edge of the bean bag.
Dennis's car is described as a 1979 AMC Gremlin. However, there is no such thing as a '79 Gremlin. The final model year for the AMC Gremlin was actually 1978.
When Zack tries to buy beer, the cashier states that you have to 19 year old to purchase it. The film takes place in Pennsylvania. The legal age to purchase alcohol in Pennslyvania has been 21 since the end of prohibition (1933). Furthermore, they purchase beer in a supermarket. In 1994, PA did not allow the sale of beer in grocery stores and supermarkets.
When Zack (Andrew Keegan) tries to buy beer at Howie's grocery store with his fake ID, he's told by the clerk that the drinking age is 19. Ohio was the last state in the U.S. to have a drinking age of 19 when it was raised to 21 in 1987
When first finding the old car you see the front end which is a 1955 Chevy, at the end they show the car restored but it at that time clearly was a 1956 Chevy.
Camp Nowhere is supposed to be located in Pennsylvania. No tropical plants or palm trees would be found in Pennsylvania due to the freezing winter temperatures.
When the two kids are arguing over whether to blow up Minneapolis or Milwaukee they finally settle on Milwaukee. But when they blow it up, the TV shows a shot of northern Minnesota.
When Zack tries to bluff his way out of buying beer with a fake I.D., he tells the clerk his father is badly handicapped and waiting in the parking lot. Shortly after, he gestures to Dennis, who is standing close by, and claims Dennis is his father. The clerk doesn't question how his handicapped father got from the parking lot to the store so quickly.
Near the end of the film, the kids go to great lengths to keep their parents away from the camp. But if the parents were able to find the camp, the kids must have told them where it was located, which makes no sense if they wanted them to stay away from it.