Continuity mistake: When Alvin is making the big SOS sign, one shot shows the whole beach and Simon and Theodore are in the middle of the big letter O. In the next shot, they are at the O's edge.
Continuity mistake: At the end of the first film Mumble has lost most of his down, because his bow tie has yellow markings, however in the second movie he has somehow grown his down back.
Continuity mistake: When Ren is dancing at the drive in, he starts dancing with a girl then stops to watch her. When he starts dancing again he moves slightly in front of her in the shot. Then in the next shot they are side by side.
Continuity mistake: The giant maker compound was purple when Franqcuer was created, but it turned orange when Lucille made another giant flea.
Audio problem: In Notes II, Madame Giry voice is out of sync as she says,"Fear his fury.".
Continuity mistake: Angela brings Katie the gift box; when she 'ta-daa!'s and Katie reaches for it, it's turned 180° compared to when Angie put the box on the bed. (00:29:20)