3.Mischa Barton's most famous role to date was none other than Marissa Cooper in The O.C.
And here's what she looks like now.
4.With over 150 episodes of Gilmore Girls under her belt, Alexis Bledel will always be Rory in our hearts.
And here's what she looks like now.
5.Leighton Meester reigned as queen bee of the Upper East Side when she transformed into Blair Waldorf on Gossip Girl.
And here's what she looks like now.
6.Shailene Woodley portrayed Amy Juergens on The Secret Life of the American Teenager, which also happens to be the longest recurring TV role of her career.
And here's what she looks like now.
7.There couldn't have been a Seth and Summer saga without Rachel Bilson joining The O.C. cast.
And here's what she looks like now.
8.Kristen Bell spent many years cracking cases in Veronica Mars.
And here's what she looks like now.
9.It's a bird, it's a plane — actually it was just Tom Welling as Clark Kent in Smallville.
And here's what he looks like now.
10.Heroes brought us "save the cheerleader, save the world," along with Hayden Panettiere as Claire Bennet.
And here's what she looks like now.
11.You might remember Adam Brody as the nerdy sweetheart Seth Cohen in The O.C.
And here's what he looks like now.
12.If you were hooked on Lost throughout the '00s, you already know Evangeline Lilly was famous for her role as Kate Austen.
And here's what she looks like now.
13.There was no better version of Ryan Atwood than Ben McKenzie's version in The O.C.
And here's what he looks like now.
14.Taylor Kitsch spent a number of years portraying Tim Riggins in Friday Night Lights.
And here's what he looks like now.
15.While Arrested Development came to an end in 2019, Jason Bateman made his first appearance on the show all the way back in 2003.
And here's what he looks like now.
16.Jennifer Garner kept us on the edge of our seats during her days as Sydney Bristow in Alias.
And here's what she looks like now.
17.Neil Patrick Harris spent nearly a decade of his life playing Barney Stinson on How I Met Your Mother.
And here's what he looks like now.
18.There was never a dull moment when you had America Ferrera on screen in Ugly Betty.
And here's what she looks like now.
19.Finally, Steve Carell couldn't help but make us all laugh in The Office, and still does today thanks to all of the regular reruns airing each week.
And here's what he looks like now.
Who was your favorite '00s TV actor? Tell us in the comments!
