BAM. This girl once played a kid spy, and we have a feeling that she walked away from her role as Carmen Cortez with more than a few sneaky tricks up her sleeve. Alexa Vega’s beauty at a grown-up 23 can only be rivaled by her stealth, because we really didn’t see that one coming.
Our favorite child doctor from the early ‘90s has grown up to play womanizing smooth-talker Barney Stinson on “How I Met Your Mother,” but we don’t mind his vulgar jokes when he looks that good in a suit and tie. Neil Patrick Harris still has the same half smile and expressive eyebrows, but age has been good to him — 40 has never looked better.
Everyone remembers her breakout role as Hermione Granger, the frizzy-haired bookworm who starred alongside Daniel Radcliffe and Rupert Grint in the Harry Potter movies. But who would have thought she’d grow into the classic beauty she is today? At 22, Emma Watson turns heads, and she didn’t have to use her wizard smarts to concoct a potion for that.
Someone please explain to us how a dorky kid from the Disney Channel ended up as Megan Fox’s love interest? Luckily it seems like some of her good looks rubbed off on Shia LaBeouf, who suddenly has a defined jawline and sense of style. Who doesn’t appreciate a guy with good looks and a sense of humor?
Remember the precious little girl who brought us all to tears in “I Am Sam”? Her blond locks and stunning blue eyes remain, but she’s all grown up now, and taking on roles like that of a heartless vampire in the Twilight movies.
Oh, Neville. You sure had us fooled. It’s hard to believe that Matthew Lewis was once the young star who once played the pudgy, pubescent Neville Longbottom in the Harry Potter films. He seems to have undergone a radical transformation overnight from an ugly duckling to the swan we’re now swooning over. Harry, Ron, step aside. We’re coming for Neville.
Jessica Biel got her start playing the role of big sister Mary Camden on "7th Heaven," and has only gotten more heavenly with age. As if being 30 and ravishing wasn’t enough, she’s also engaged to Justin Timberlake. She grew up on us so fast!
Even with his terrible hairstyle and laughable ‘90s wardrobe in “3rd Rock From the Sun,” Joseph Gordon-Levitt was always adorable. But suddenly there he was, looking suave and getting his heart stomped on by Zooey Deschanel in “500 Days of Summer,” and every woman watching went weak in the knees. By far, one of the most impressive transformations we’ve seen.
It may come as a surprise to teenage girls that Taylor Lautner had a long career before “Twilight.” It wasn’t until he cut his hair and buffed up as werewolf Jacob Black that young Twihards began screaming at the sight of him.
This little redhead once charmed us with her mischievousness in “The Parent Trap.” Lindsay Lohan has faced some challenges, but there’s no denying that she was the “it” girl for a while. Back when she had those bodacious curves, Lohan was a vision in red.
Remember Adam Sandler’s little friend in "Big Daddy"? That’s Cole Sprouse, who went on to star in the Disney hit series "The Suite Life of Zack and Cody." Sprouse, now almost 20, boasts a rockin’ beach bod. Cole, we’d live the suite life with you anytime.
Mary-Kate and Ashley Olsen stole our hearts at the age of one with their dual effort in playing the adorably sassy Michelle Tanner, and their success has hardly faltered since. Now in their late 20s, the sisters have become fashion icons, launching their own couture fashion label, and wearing it well.
Zac Efron is like a bottle of fine wine; he just gets better with age. He went from a loveable gap-toothed kid in "Summerland" to a dreamy, crooning jock in "High School Musical" and every appearance since has been equally swoon-worthy.
Kids — they grow up so fast. From the dorky but loveable Joseph Gordon-Levitt in 90s sitcom "3rd Rock from the Sun" to the adorable Dakota Fanning in "I Am Sam," many of our beloved child stars have since bloomed into, well, extremely attractive human beings. While those like former "Doogie Howser, M.D." star Neil Patrick Harris carry their youthful aura while still managing to be incredibly handsome, others, like Alexa Vega of "Spy Kids," look completely different, and completely sexy.
Look through the gallery above to see the most jaw-dropping transformations in our favorite former-kid stars.