Continuity mistake: At the end of the first shot of Lardass drinking castor oil, the bottle is nearly full, but at the start of the next shot, the bottle is nearly empty. Because of the people talking in the background, they couldn't have cut forward to the part where he is finishing.
Continuity mistake: During the mailbox baseball scene, Ace is shown with a cigarette in his mouth. Then after he strikes out and says "ah shit, I'm out", the cigarette is gone.
Continuity mistake: About half way through their journey the boys clothes are very dirty, then they become spotless.
Continuity mistake: In the beginning scene, the newspaper clipping under the headline shows the first sentence to be about Chris' death from a stabbing, but the next line starts mid sentence about a completely different subject and the second column under the headline talks about taxes, mentioning nothing about the death.
Continuity mistake: When the boys are in the treehouse at the beginning, the coca cola bottle on the treehouse shelf constantly moves places between shots. The two sides of the bottle saying "coke" and "coca-cola" keep switching positions between shots also. (00:02:55 - 00:04:55)
Continuity mistake: Watch carefully in the scene where the four boys are running for their lives over the railway bridge. Chris and Teddy are in front, and Vern and Gordie are behind. In one shot we see just Vern and Gordie's feet, and quite a lot of the track behind them. You can see that there is no train behind them. In the very next shot, the train is about two metres behind them