you can buy an oversized blue turtleneck paint the tip of the nose black, this works well if you can get three kids together and do all three chipmunks. You can stuff the turtleneck if needed by taping bags to the inside of the costume and filling them up with whatever you can find that will remain soft and not weigh the child down. The same concept would go with the other two chipmunks, for Alvin you could buy yellow felt make an A and attach it to the red shirt, Theadore you would just find a cheap pair of glasses to put on with his green shirt.
