Live-action stars take a backseat to CGI chipmunks in this uneven family comedy: Alvin, Theodore, and Simon have the only good lines or recognizable emotions, with Jason Lee and David Cross straining to flesh out their cardboard roles. Lee plays a struggling LA musician who hits it big with a Christmas track featuring the three singing rodents; Cross is a venal music executive who tries to cut him out of the action. The jabs at merchandising are pretty cynical, given that the title characters have been a cash cow for producer Ross Bagdasarian and his heirs since he created the act in 1958. Tim Hill (Garfield: A Tail of Two Kitties) directed. PG, 91 min.