Continuity mistake: When Napoleon drops off the drawing of Trisha with her mom, he is standing on the porch. He then says 'bye' and runs off of the porch. The next camera shot is from Trisha's mom's perspective of the screen/glass door closing. When the door is closing you can see Napoleon's reflection in the glass (he's standing right there when he should have been far away from there if he had run off the porch as portrayed).
Continuity mistake: When Napoleon starts his dance skit near the end of the movie, his t-shirt is tucked into his pants. Shortly into the skit, the shirt comes loose in the back and on one side. A few seconds later, the shirt is once again completely tucked in. This happens several times throughout the scene.
Continuity mistake: When Summer and Trisha are handing out "vote for Summer" fliers, in the close up of Summer handing them out you can see that one of the girls has on pink nail polish. Moments later, in a shot from a further distance (yet close enough to see nails), neither girl has on any pink nail polish.
Continuity mistake: When Napoleon, Grandma, and Kip are all in the kitchen area, in the shot of Grandma leaving, the container is nowhere close to the counter top edge and next to what looks like a phone book. Two shots later, in a close-up of Kip, the same food is now close to the counter top edge with the phone book nowhere to be seen. As the two argue in different shots, the container of food moves back and forth. On top of this, the phone book that was there in the original shot has mysteriously disappeared from every subsequent camera angle.
Continuity mistake: When Uncle Rico hands Trisha and Summer the "Bust Must" fliers, at the end when they show a close up of them reading it, there are two sets of hands holding up the paper. However, in the shots both before and after, Trisha is only holding up the flier with her right hand.