Continuity mistake: After getting off the school bus, when Gus falls into the hole that Sam has dug in front of the school, he's wearing his watch as usual. As Gus sits up, his watch vanishes mid-shot; then it reappears on his wrist.
Continuity mistake: After Upside-Down Girl tells TJ he must do something about Dave, when the gang look for Sam and discuss the situation with him, the clock over the school doors repeatedly changes time between shots. Then, when Sam grabs the shovel and jumps back into the hole, the two hands of the clock vanish, only to reappear and change time yet again.
Other mistake: At lunch, when Sam is using a spoon to shape his mashed potatoes on the tray, his right arm clips through the tray just as he says, "Maybe I should clear out the east wall like this." Then, when Sam says, "Maybe I should fortify the south side first," he's using the spoon to move the mashed potatoes on top of the tray, but his arm and spoon are under the tray, so it looks as if the potatoes move on their own. Additionally, when Sam states that he's so confused, the spoon held up in his right hand appears to vanish in the next shot.
Continuity mistake: The gang hatches a plan and tells Dave that Sam is trapped in a cave-in, so Dave begins digging to save him. When Sam and Spinelli return with their ice cream cones, Sam's gloves vanish and reappear a couple of times while he is holding his ice cream.
Other mistake: When the Ashleys are playing jacks, Ashley B is wearing her usual yellow sweater, but in the next shot, it becomes red, the wrong colour. It goes back to yellow in the next shot.
Factual error: After Digger Dave and Digger Sam split up, they show that Sam was unfocused and was digging everywhere. Even through concrete?
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.
Schoolworld - S4-E21
Continuity mistake: The door to Miss Grotke's classroom opens inward throughout the episode. However, when SAL mimics Principal Prickly and tells all the teachers to report to his office, Miss Grotke leaves the classroom, and the door now opens outward. Then, when the kids look outside the classroom, the door has completely vanished.
Schoolworld - S4-E21
Continuity mistake: When Gus gets locked out of the school after recess, he asks SAL to open the hallway door. He looks up at the clock, and the time on it is 10.46.05 (then goes up to 10.46.08 by the end of the shot). A few seconds later, the time changes to 18.46.16, then 10.46.17, then 10.45.18.
Factual error: When Menlo is hoppin' scotch, he lands on 10 with both feet, and 10 is a single square.
Suggested correction: He does, but this is simply a mistake Menlo makes as a character. And it is not a 'character mistake'; I can see many people making a very simple mistake like this while playing hopscotch. I know I probably have as a kid. Also, he lands on an 8 square, not a 10 square.
Audio problem: When Randall says, "Way to hop, man." his mouth doesn't move when he says 'man' until after he's finished saying it.
Continuity mistake: When Randall begs Gretchen to do his homework, Mikey says, "Tutoring is just another word for helping," and his backpack is green. A few seconds later, it changes to blue.
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.
Spinelli's Masterpiece - S4-E27
Revealing mistake: When the hosepipe bursts and Spinelli's picture gets ruined, the water rises up a few inches off the ground, but the school has a chained fence so the water should run out.
Bonky Fever - S4-E30
Other mistake: When T.J. goes to Miss Finster to tell her about Mikey's Bonky stuff, Miss Finster's waistband is yellow when it's supposed to be white. Then, when she takes the bag from T.J., it has changed to pink, then turns white and back to pink mid-shot. Her collar is also yellow in this shot, then turns white and back to yellow mid-shot as well.
Bonky Fever - S4-E30
Continuity mistake: When the gang arrives at Mikey's house with his birthday gifts, Gus wears a red bow tie. Then, when the gang walks up to the door, Gus's bow tie has changed to the same color as his shirt, then goes back to red in the next shot.
Bonky Fever - S4-E30
Continuity mistake: When the gang arrives at Mikey's house with his birthday gifts, note the colours of the gifts that Gretchen and Gus are holding. When the gang looks at Spinelli's gift, Gretchen and Gus's gifts have swapped colours, then they swap back in the next shot.
Bonky Fever - S4-E30
Continuity mistake: In the cafeteria, Mikey asks the lunch lady for more pudding for Bonky. When the lunch lady refuses, the clothing on Mikey's Bonky puppet has vanished, then it reappears in the next shot.
Bonky Fever - S4-E30
Continuity mistake: After the gang gives Mikey his backpack full of Bonky stuff, Mikey runs away from them, and he is heading towards two kids playing marbles. Then, when Mikey slips on the marbles, they have changed colour.
Bonky Fever - S4-E30
Continuity mistake: After the gang finds out that Mikey was sucking on a Bonky pop, they find his backpack, which is its usual green colour. Then, when they discover all of the Bonky stuff inside it, it has changed to red.