If you watched the MTV Movie Awards on Sunday you probably haven't been able to get the shirtless image of Zac Efron out of your head (we know we haven't!). It seems like the nerdy child star, who used to star in the TV show Summerland with Jesse McCartney before moving on to High School Musical, became a total heartthrob overnight.

In honor of Zac's ab-tastic acceptance speech at the Movie Awards, we're dedicating today's Transformation Tuesday to him and all the other nerdy child stars who became hotties! Click through, then let us know whose transformation shocks you the most in the comments below.

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