Rachel Bilson turns the big 3-0 today, and we're celebrating the milestone with a look back at her cutest moments with her many costars and collaborators, past and present. From her early days growing up on the set of The OC, to her latest turn on the small screen in Hart of Dixie, Rachel has forged lots of fun memories with her fellow actors. She dated her onscreen love, Adam Brody, and later found romance with Hayden Christensen, her Jumper costar. She's also found lots of female friends through her small- and big-screen projects over the years, from Mischa Barton to Kate Bosworth. Rachel's even teamed up with Karl Lagerfeld, who directed her recent ad campaign for Magnum ice cream. Click through our gallery for a look at Rachel sharing sweet moments with her costars and friends over the years!