Deliberate mistake: While the rock n' roll musical is ending, it shows the hot air balloons in the background and it shows Dave up close. He talks to himself confused, trying to figure out if he really saw his boys there or not. But if not being able to notice, wouldn't he at least hear them singing in the background as well as we can? Also, before, while Alvin and Britany were dancing together, he was trying to get to them before the two bad guys could, as if he knew for sure they were his boys and that those guys were out to get them.