Say "Aaawww!" The adorable chipmunks created by Ross Bagdasarian first appeared in 1958 and have chirped through recordings and animated TV specials ever since. But they only recently entered the 3-D realm of computer graphics, thanks to the surprise Fox hit "Alvin and the Chipmunks." When it came to updating the sweater-clad trio, the mandate from director Tim Hill was reality. "He wanted them to look like real chipmunks, and still maintain their cutie aspect," says visual-effects supervisor Todd Shifflett ("Babe," "Happy Feet"), who oversaw some 500 chipmunk shots by animated animal specialists Rhythm & Hues.