It's hard to believe that chipmunk siblings Alvin, Simon and Theodore are about to hit the half-century mark; in fact, they look younger than ever in their CGI feature film debut, "Alvin and the Chipmunks."

It's been close to 50 years since Ross Bagdasarian borrowed the sped-up voice he'd invented for his ting-tang-walla-walla-bing-bang novelty hit "Witch Doctor" to create the trio. The Chipmunks shot to stardom with their own No. 1 hit, 1958's "Christmas Song," and have been around ever since. Bagdasarian died in 1972, but his son Ross Jr. and Ross' wife (and the movie's co-producer) Janice Karman know what it takes to keep the Chipmunks on the charts.
"The personality clash between Dave Seville, the manager and parent figure, and Alvin, the kid who just won't take no for an answer, is the reason we're here almost 50 years later," says the younger Bagdasarian, making Alvin sound like a furry Bart Simpson.

During that half-century, the Chipmunks have covered rock, punk and country songs while appearing in two TV series, an animated feature film (1987's "Chipmunk Adventure") and several direct-to-video releases.

After performing as hand puppets with Ross Sr. on "The Ed Sullivan Show," the trio got their first makeover as stars of their own 1961 prime-time CBS series when they donned the oversize sweatshirts that would serve them well for the next 45 years. The Chipmunks underwent a cuteness upgrade for their 1980s Saturday morning TV show, evolving from flatly drawn cartoon figures into chubby-cheeked moppets who dominated Saturday morning television in the '80s.

Boomers and thirtysomethings who remember those Chipmunks may be in for a bit of a shock when they see the trio's newest incarnation. "Janice and I wanted to put them in the live-action world," Bagdasarian explains. "But if you went with the cartoon style, not only would they have a flat 2-D look, they would come up to Dave's waist. All of a sudden it would be 'Attack of the Killer Chipmunks.'" Instead, Alvin and his brothers have been downsized to nonthreatening height for their CGI debut, and they've traded in their baggy sweatshirts for more fashionable hoodies and headwear brimming with street 'tude. Even so, they're more charming than ever, with big round eyes and furry tummies peeking out from under those hoodies. Their personalities have been fleshed out as well, with Simon (the one with the glasses) looking out for baby brother Theodore while trying to keep the impetuous Alvin out of trouble."Some people involved in the movie wanted them aged up, with a teenage sensibility," Bagdasarian says, "but the charm of them is what comes out of their mouths is snappy, sassy, yet they look like the little kids they really are."