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21 & Under: Hottest Breakout Stars
Zac! Rihanna! Shia! Lauren! These kids aren't only the most popular, they're also the most likely to get bigger in '08. By Aaron Parsley
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THE HEARTTHROB
With the worldwide sensation High School Musical 2 breaking records and his big screen debut in Hairspray, Zac Efron, 20, proved that he's going to be making girls scream for a long, long time.
