Rachel Bilson, last seen saying goodbye to "The O.C.," will help out former boss Josh Schwartz on one of his new shows.

Bilson will do a guest-starring arc on NBC's new series "Chuck" this fall, Schwartz told reporters on a conference call Thursday. She'll be playing a potential love interest for the title character, tech-support worker turned spy Chuck Bartowski (Zachary Levi).

"She's going to do a couple of episodes," Schwartz says. "We're thrilled it worked out. She was off doing this giant Doug Liman action movie ['Jumper'] all over the world and was going to be in L.A. for a few weeks.

"She's really, really funny, and we felt like she could really fit the tone of the show. We thought the chemistry she'd have and the comedy between her and Zach seemed ideal. So we're really excited she was around and available and willing to help out our little show as we get launched."

Bilson's character, who will first appear in the show's seventh episode, will be a sandwich-maker who hits it off with Chuck. Things seem great at first, but since the series is about Chuck trying to manage a double life as an underpaid big box-store employee and high-value government asset, he starts to wonder if she's really who she says she is.

It also puts a strain on his relationship with Sarah (Yvonne Strahovski), the CIA agent assigned to watch over him. "It creates a nice dynamic between Chuck and Sarah as they try to figure out what's real and what's just cover," Schwartz says.

"Chuck" premieres at 8 p.m. ET Monday, Sept. 24 on NBC.