Continuity mistake: The amount of blueberries and sauce on Lardass Davey Hogan, before he vomits, changes from shot to shot. (00:46:10)
Continuity mistake: Towards the end of the movie just after Gordie has scared off Ace and the gang, Gordie turns his head towards Chris when his friend repeats the "suck my fat one" insult. When the camera cuts, Gordie's suddenly facing forward again.
Revealing mistake: In the train scene, River Phoenix's voice has suddenly changed and he looks older. This scene was obviously shot last, and he has started going through puberty. But in terms of movie time, he has gone through puberty in two days.
Continuity mistake: When Gordy returns to the junkyard after getting the food he sees his friends running away. The junkman yells at him and Gordy starts running away towards the fence. In the background he passes the same junk vehicles multiple times. (00:26:15)
Continuity mistake: When Gordie jumps over the fence away from Chopper and they all realise he's not fierce, the boys start to tease him. While Teddy's saying "Bite my ass, Choppy" the dog bites through the fence and Teddy pulls away, and then in the next shot he pulls away again and jumps differently.
Factual error: When Gordy goes to get supplies at the store, as he is standing there the clerk is talking about Denny, and in the background on the shelf there is a bottle of Soft Scrub. It's supposed to be the 1960s, but Soft Scrub was not around until the early 80s. (00:25:00)
Continuity mistake: When Chris gives Gordie the loaded gun and it goes off behind the diner, they run away around the corner and Gordie get really mad Chris tricked him. Chris stops Gordie in front of a pale beige wall, and then when Chris tells him he didn't know it was loaded, they are in front of a glass window.
Continuity mistake: When the boys are at the junk yard and they nominate Gordy to get the food, when Gordy jumps up and starts joking with the boys, Vern and Chris start to fight. Then the shot changes and suddenly Teddy, who was off to the side, is in the middle of the pile. (00:23:35)
Continuity mistake: In the treehouse, Gordie has a hair dangling over his forehead. But at the end of this scene, when they decide whether or not to go get the body, Gordie says "Sure," and the hair over his forehead is gone and his hair is neat and combed.
Continuity mistake: Gordie's hair constantly changes throughout the film from floppy to gelled, i.e. in the scene on the trestle over the water he yells, "Train!" and his hair appears to be quite dry, without a parting. In the next short scene around the campfire, it looks perfectly combed and gelled. He can not have borrowed Vern's comb, since Vern lost it on the train bridge.
Continuity mistake: When the four are deciding whether to cross the swamp, Chris pulls off a nearby tree branch to test the deepness. First the branch is quite flimsy and has two ends like a "Y" shape, and then after Chris pokes it into the marsh it becomes thicker with no split end.
Continuity mistake: When the boys are up in the treehouse at the start of the movie, at one point Chris blows out some smoke into a cloud in front of him, but in the next shot it's completely disappeared.
Continuity mistake: In the first shot of the scene where Gordie has a flashback of his family at the table, we see two pieces of corn near his plate. In the next shot of Gordie's plate, the pieces of corn are gone.
Visible crew/equipment: There is a boom mike clearly visible in the billiard scene. [Edited in DVD]
Continuity mistake: The blood on Gordie's hand change from shot to shot when he finds the leech downstairs, from being over most of his three middle fingers, to the ends of his index and middle, then to being all over again.
Continuity mistake: In between shots of Lardass as Gordie says "By the time he was on his fifth pie, Lardass pretended that he wasn't eating pies.", the crust on Lardass' forehead disappears.
Revealing mistake: Not to say Lardass was thin, but it is very clear that his shirt is stuffed up with some kind of padding to make him appear very obese, when he is announced for the pie eating contest.
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.
Other mistake: In the treehouse scene, Teddy tells Vern that nobody will care if they didn't go to the drag race. When Teddy says this you can see Chris mouthing his lines. (00:07:45)
Revealing mistake: In the car race scene with Ace and his gang you can see that it is not Ace driving when the car runs over the wood in the road.
Answer: A cello.