Alvin, Simon and Theodore are back, along with their stressed-out manager, Dave. But this time they've got competition: The Chipettes.

To everyone's surprise, including his own, Po, an overweight, clumsy panda, is chosen as protector of the Valley of Peace. His suitability will soon be tested as the valley's arch-enemy is on his way.

Talented chipmunks Alvin, Simon and Theodore become singing sensations when they meet struggling songwriter Dave Seville, who becomes their manager.

When their relationship turns sour, a couple undergoes a medical procedure to have each other erased from their memories for ever.

With aliens once again threatening Earth, Agent J will need to refresh his partner's memory and get them both ready for a high-octane mission.