Best of 2007

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

THE COMIC RELIEF

After a brilliant run as the awkward George Michael in the fan favorite Arrested Development, Michael Cera, 19, graduated to the big screen with the super hit Superbad, a raunchy teen movie antithesis to Disney's High School Musical that even had the New York Times acknowledging his "deceptively innocent eyes." Now this winter the nerdy cute boy will get serious in the teen pregnancy indie film Juno, costarring Jennifer Garner and Jason Bateman.