Continuity mistake: In the scene where Dewey and Ms. Mullins are in the bar, the shots from behind Ms. Mullins sitting down show that her left hand is on the table. However, the shots showing the front of Ms. Mullins show her arms folded.
Other mistake: After the concert, when Dewey is telling Gordon how awesome the lights were, Eleni calls him Jack. The actor that plays Dewey is Jack Black. (This mistake is mentioned in the Kids Kommentary [sic].)
Trivia: Miranda Cosgrove, who plays Summer Hathaway, actually has a really good voice and plays guitar. She had to take a 45-minute class to learn how to sing badly for the one scene where she sang "Memories."
Dewey: Billy what makes you angrier than anything in the world? Billy: You. Dewey: Billy, we've already told me off, now let's move on. Billy: You're tacky and I hate you. Dewey: Ok, you see me after class!