Continuity mistake: Once the chipmunks are inside the food cupboards, they begin to devour everything inside. Theodore is seen chewing off a corner of a box of Lucky Charms cereal and eating the cereal that pours from the hole. But a few shots later when the same box of cereal can be seen, the hole that Theodore gnawed from the corner of the box is gone and the corner is fully intact. (00:11:00)
Continuity mistake: When Sophie and Alex are in the cafe the camera shows Alex from behind Sophie, and Sophie picks up a drink in the very next shot she has put it down. This happens throughout the scene in the cafe with her hands. (00:35:30)
Revealing mistake: When Dewey is singing the protest song about midgets in 1966, modern cars can be seen driving in the background.
Factual error: When August sits down at the piano in the church and begins to play, he plays a passage of ascending notes (his hand is actually on camera so you see it move to the right, up the piano). However, the audio that you actually hear is a passage of descending notes.
Factual error: The phone at the Peacocks house is too modern for the time - the cord going into the handset had a clip in cord versus being attached directly to the piece.
Revealing mistake: In the jazz club, the saxophone player's finger movements don't match what he is playing.
Factual error: At the end of the movie, Pat is watching a news report about John Lennon's death, which is intercut with scenes of Darby making preparations for his fatal overdose. Darby died almost a whole day before Lennon's assassination.
Factual error: When the girls talk at the beginning of the movie, they can fully hear and understand each other even when they are at massive distance from the webcams they are supposedly using to communicate.