Each box the father takes out dumps a ton of cereal out of the bottom backs of the boxes. When Lane visits his brother's room to talk to him, his brother is working on a model gun. We see the brother tooling on the gun with a screwdriver, but there's no screw. In the cafeteria scene, where Lane tries to pick up a cheerleader on roller skates, he chases after her to the lunch line, borrowing someone's skates along the way. He must have put them on awfully fast, because even though she got to the very short lunch line ahead of him and there was only one person in front of her, she was only JUST getting her milk when he finally arrived.
Roller skates take a while to lace up.
Lane accidentally puts the car in reverse and crashes backward through the garage doors. I'm no expert, but I would think that you couldn't obliterate the entire two-door garage door with only a foot of space to work with. At the end of the movie when the French girl and Lane are at Dodgers Stadium you can clearly see bike tracks in the dirt and grass where the paperboy had ridden in previous takes. In the scene where Lane's mother pulls him into the dinning room for dinner with the neighbours, Lane's father is at the head of the table and has nothing on his left shoulder. The camera slightly cuts away from the father and when it cuts back the father is suddenly pulling a cloth his left shoulder that was never there before.