Revealing mistake: Right after TJ and friends are looking at the "thermometers" of cans, the Ashleys have at least 4 crates of cans that they bring in on forklifts. However, the end result is 4,362 cans for the Ashleys. This may seem kind of picky, but I think there was more cans than 4,362.
Plot hole: Hustler kid tells Gus in this episode that hustlers never deal in things that could get a kid in trouble. In the episode where all the kids need to become Ashley's he has no problem in handing out plenty of fake IDs, and at the beginning of every show he is shown displaying dodgy merchandise to a kid inside his jacket.(the kid isn't inside the jacket...the merchandise is...).
Spinelli's Masterpiece - S4-E27
Continuity mistake: When the kids are all on the jungle gym to see Spinelli's drawing, Jerome can be seen sitting on the bar of the swings. However, when everyone is cheering he has suddenly moved to the ladder.
Here Comes Mr. Perfect - S4-E18
Continuity mistake: When Jared is holding his speech, Jerome's jumper turns blue twice.
Omega Kids - S2-E16
Continuity mistake: When TJ tells Vince to throw him a pepperoni pizza, Vince has two pizzas - one in his hand and one on his plate. In the next shot the pizza on the plate has vanished.
The Legend of Big Kid - S1-E14
Continuity mistake: At the end of the episode, when the gang is caged, right after Vince gives TJ the baseball card, TJ's facepaint turns from blue to red, then back to blue. (00:08:35)
Continuity mistake: When Randall's dad is talking to the gang about what Randall's been telling him about them (when they are outside, in front of the bouncy thing), his moustache disappears mid-sentence (in a close-up of him) and reappears in the next shot.
Factual error: When Stuart escapes and jumps out of the classroom the clock reads 9:00. but after Mikey runs out to go get him the bell rings immediately after. Recess wouldn't be that early.
The Secret Life of Grotke - S4-E32
Continuity mistake: When the gang are sat at the table before Miss Grotke comes on, the table is empty, but when Miss Grotke comes on stage, they suddenly have drinks.
The Spy Who Came In from the Playground - S4-E4
Other mistake: When the gang is showing stone their way into the school they go through a vent and all of them manage to squeeze through the small hole in the wall.
Continuity mistake: When Randall and TJ are walking across the playground, Randall's hair has turned black and so has TJ's hat.
Continuity mistake: When Gretchen is playing with corn chip girl she puts down a card which is the orange cheetah. Yet after she has talked to TJ, it has suddenly changed to a completely different animal.
Chez Vince - S4-E41
Continuity mistake: In the cafeteria, TJ is wearing a suit to welcome the customers. But when he and the rest of the guys go to the teacher's lounge he's back in his normal clothes.
The Spy Who Came In from the Playground - S4-E4
Continuity mistake: After the part where Mikey gets double portions, the school clock shows it is half past one, but a couple of shots later shows the clock at half past ten, what kind of clock does that?
Continuity mistake: At the very beginning, Gus drinks his entire carton of chocolate milk. Then in the wide shot, his carton is white. Back to a close up, and it's brown again.
Continuity mistake: When Agents Barnes and Noble are passing out the test, there is a boy in a green hat sitting in front of a girl with long hair. The next shot is of the same boy asking if he can use a pen, but now there is another boy with blond hair right behind him.
Continuity mistake: When the gang is eating lunch, there is a girl in a pink shirt and some other people at the table behind them. When it cuts to behind Prickley and TJ, the kids at that table are different.
The Spy Who Came In from the Playground - S4-E4
Continuity mistake: When the superintendent arrives at the school, he looks towards Stone who gives him a thumbs up. When he does this, Stone and the group around him are on the steps right in front of the entrance to the school. A couple of shots later, the entire group has suddenly appeared in front of the window without time for all of them to have moved.
Continuity mistake: After it is explained that without Dave, Sam is unfocused, you see that he has dug holes just about everywhere. However, after that scene, all the holes disappear.
Continuity mistake: After T.J. has become principle for a day, it shows him chewing out a kid for running in the halls. He throws down a manilla folder onto his desk in anger. However, when the shot changes, the folder has disappeared.
