In a rare moment of generosity, Alvin gives his beloved cap to a fan. But soon he's convinced his mojo was in his cap, and must find a way to get his hat back before the Chipmunks' big concert./During a costume visit to the zoo, Alvin finds himself mistaken for a real Tasmanian devil. Soon, Alvin is stuck in the Tasmanian devil's cage and the real animal, goes home to the Sevilles'. The mix-up creates problems all around, especially when Simon reads that the Tasmanian devil is scheduled for surgery. Can Dave and the boys get to Alvin before the operation?!