Bilson became a breakout star thanks to the cult teen drama, and she returned to her roots at The Montalban Theatre in Hollywood to watch the one-night-only staging of The O.C. as a musical.

Bilson, who marked her first red carpet appearance since giving birth to her first child last year (Nov14) at the event, was joined by Kelly Rowan, Melinda Clarke, show creator Josh Schwartz and executive producers Stephanie Savage and MCG.

The gang watched original The O.C. cast member Autumn Reeser, who took the stage as Clarke's Julie Cooper character, and the rest of the cast revamp storylines from the pilot, as well as series iconic moments through songs which featured prominently on the show including Oasis' Champagne Supernova, Hallelujah, and California, the memorable theme song by Phantom Planet.

Other stars taking on The O.C. roles at the sold-out performance included Australian pop star Betty Who, Pretty Little Liars actor Brendan Robinson, actor/singer Drew Seeley and Kelsey Grammer's actress daughter, Greer Grammer.