Continuity mistake: On top of the white cabinets / cupboards that run along the kitchen is a whole row of glass jars, vases, pots, etc. During the whole kitchen scene, the actual jars and pots that are on top of these cabinets move around and rearrange in different shots. In the close-up of Alvin pushing over the packet of Cheese Balls for instance; you can see that the jars and pots on the cupboard above are differently arranged than in other wide shots of the whole kitchen. (00:11:15)
Answer: He knew that if he impressed Ian, he and the Chipmunks would become rich and famous. When they froze, he looked like a lunatic who thought animals could talk, making him appear foolish in front of a man who already had little respect for him.
Brian Katcher