Continuity mistake: In the scene were Lloyd finds Harry's "treasure chest", you can see that the chest is laying flat against the wall, but when the Principal and the lunch lady come and find it missing, there is a small dirt outline, as if the chest was pointing out from the wall, instead of larger outline, as if it were flat against the wall.
Continuity mistake: When Harry and Lloyd first collide, if you look carefully you can see that Lloyd still has his entire tooth when he falls. It was supposed to be chipped.
Continuity mistake: When Lloyd is sticking the napkins on himself in the cafeteria, you can see he is wearing underwear under the napkins, while in the next shot he isn't.
Continuity mistake: When Jessica is chasing the bus to the museum, her hubcap comes off after she goes airborne over the hill. It is back on in the next shot.
Continuity mistake: When Ms. Heller is talking to the tour guide at the museum, she offers her a $5 bill to take the tour twice. How the bill is folded changes. When it is a close-up of Ms. Heller the bill is half folded but when the tour guide is pushing away the bill it is fully folded, then it keeps switching back between folds.
Continuity mistake: When Jessica and the principal are in his car watch the driver's side mirror. When Lloyd and Harry are following them you see a side view of the car and it has a regular teardrop mirror. After Lloyd and Harry get ice cream the principal is telling Jessica no one will be looking for her and the side view mirror has gone to a big square truck mirror like welded to the door.EMTurbo
Continuity mistake: When the bus is driving to the museum the camera goes to Lloyd and Harry. In the window you see a car passing. When the movie shows an overhead shot of the road, there is no car in front or to the side of the bus.
Continuity mistake: When Harry is drinking his Slushy fast, some drips on his neck and leaves a stain. Then, when Jessica comes, the stain is gone.
Continuity mistake: When the teacher asks her "special needs class" if they have any ideas for a float, the camera switches between people and conversations and every single time this happens the Chinese exchange student changes position (resting on her elbow, arms out stretched, hands together etc...)
Continuity mistake: Louis has a black eye from Lloyd hitting him while in his pirate costume, as Lloyd finds out when he is wearing the "polar wear". Then, in the special needs class that same day, we see Louis without the black eye.
Continuity mistake: When the special needs class is debating a float, look at the chalkboard in the background. The word 'float' is underlined, then the next time you see it, it isn't underlined. This occurs a number of times throughout the scene.
Continuity mistake: After Lloyd breaks the window with his message via a large brick, the glass on the left side of the window sill keeps shifting back and forth 90 degrees from shot to shot.