Swept up in a holiday mood, Alvin gives away his cherished harmonica to a little boy. Meanwhile, Dave has booked Alvin to perform a harmonica solo at Carnegie Hall.

Join Alvin and his brothers Simon and Theodore for this hilarious Halloween adventure. Alvin wants to be accepted into the Monster Club to get their cool monster jacket, but the monster members think it's cool to be cruel. It takes Theodore's friendship with Michael, a misunderstood outcast the other kids call Pumpkinhead, to show Alvin that being a true friend is really a lot more cool than trying to be a popular monster!

The vacationing Chipmunks and Chipettes are turning a luxury cruise liner into their personal playground, until they become 'chipwrecked' on a remote island. As the 'Munks and Chipettes try various schemes to find their way home, they accidentally discover their new turf is not as deserted as it seems.