Let's talk about casting. Which parts got filled quickly?
Josh Schwartz: Peter Gallagher was first. When I first wrote the script the Cohens were the Needlemans.
Too Jew-y?
Josh Schwartz: Too Jew-y. I was like, “Jeff Goldblum in a wetsuit!” I was disabused of that notion. And we heard Peter was looking to do series TV and I still remember the first time we met him, him running through the lines with us. And it was incredibly exciting because I never had an actor of his caliber read anything that I'd done before. And we wanted to send a very clear message that this was a show as much about the parents as it was about the kids, and we had this acclaimed film and stage actor in the lead role, heartthrob himself. And somebody who was a terrific actor who was going to ground the adult world with a lot of credibility. 
I don't really remember the exact order moving forward, but we struggled casting the kids. Rachel (Bilson) was easy to cast 'cause she was a guest star, so she didn't needed to be approved; she had three lines. The two finalists for Marissa were Mischa (Barton) and Olivia Wilde. And we loved Olivia. She had just moved here I think from D.C. and she was brand-new, but she was obviously beautiful but also really good. The thing with Olivia is she's so strong. She's such a tough smart strong girl. That was a version of Marissa that did not need saving. And we had in mind a character with a little more of a doe-like energy and somebody who was lost and trapped and needed someone like Ryan to come in and help them be free — the princess in the tower. But with Olivia, we always knew we had to find something else for her to do.
And fortunately, “Skin” got canceled.
Josh Schwartz: That was the first time Fox saw her, when she read for “The O.C.” And when Mischa ultimately got the part, they put her in “Skin.” The first chance we had to get her, we created that part for her. With Seth, we saw a lot of kids. Some that we referred to as “bar mitzvah Josh” because they were like the too real version. The version that felt too much like what I was like in high school — nobody wanted to see that kid losing his virginity. And Adam, when he first came in, he was auditioning probably for 10 or 12 pilots a day, didn't bother to learn basically any of the lines for his audition scene. I was even like, “What scene is he doing; is this from our show? What is he doing? I hate this kid; get him out of here.” And then we couldn't find Seth and our casting director, Patrick Rush, was like, “We should bring back Adam Brody.  I'm telling you, there's something special about that kid.” He came back in and did a really great job. The challenge with that part was always when we were putting the pilot together and given the series Fox very much had the “90210” model in their head. I had never really seen “90210.” So Stephanie knows every episode by heart, but I hadn't really seen it. So they kept saying, “Well, if Ryan's Luke Perry, who is Jason Priestley?” And I was like, "That's not our show." And they're (worried about) this Jewish kid who reads comics and plays with plastic horses. Though he didn’t have Captain Oats at that time.
Ryan originally was going to be Garrett Hedlund. And he was gonna go in and test for the studio, and then he got “Troy,” and was suddenly not available and off to have a movie career. And we couldn't find Ryan. We couldn't find the guy who felt smart and soulful but also brought enough of that bad boy energy to the role. And Ben (McKenzie) had just auditioned for like the sixth lead of a UPN show, and we got a call from one of those casting it saying, "We saw this kid; we think he's really interesting. You should have him come in and read."  And we saw the chemistry between he and Mischa and him and Adam that was really critical to the show and they had that magic. 
Kelly Rowan was somebody who was a terrific actress who came in and, even though she was Canadian, she fulfilled that Orange County shiksa goddess quality. And then Melinda (Clarke), our worry was that she was really young to play Julie. But we were like, “She's so funny, she's going to bite into this role and give it everything but can we make her feel like she's old enough to have had a teenage daughter?” which hair and make-up allowed us to do. And then Tate Donovan we knew and we loved how likable he was. And I was single at the time and was hoping he would teach me about the birds and the bees.
And Shailene Woodley as Kaitlin Cooper.
You had Shailene Woodley as Kaitlin, and then you replaced her as Kaitlin. What happened?
Josh Schwartz: The thing you have to remember is Shailene was really little when she did the show. And she was hilarious; we loved her. She would come in with her like riding helmet on and talk about China the pony and China's alopecia. And she nailed everything, like she would see Luke at the door and give him the right look. But she was so young, it was hard to kind of keep her folded into the storyline. So we sort of moved her out and when we were looking to bring that character back having aged a little bit more quickly than was probably biologically possible for Kaitlin Cooper. We wanted somebody who could more readily kind of fold into those stores. So she was still just a bit young.
Shailene was too young to be going on dates with Chris Brown.
Josh Schwartz: Pretty much.(*) So obviously now thrilled for her and she's become a terrific actress. And Stephanie has a very funny drawing that Shailene sent us. She drew us like a picture of her and China the horse and we sill have it. But Willa Holland was the perfect person to play that version of Kaitlin at that age.
(*) After the interview, I actually looked up the respective ages, and Holland is only five months older than Woodley. Reached for comment, Schwartz insisted, “Well, she felt older. Five months is a lifetime at that age.”
Alan Sepinwall has been reviewing television since the mid-'90s, first for Tony Soprano's hometown paper, The Star-Ledger, and now for HitFix. His new book, "The Revolution Was Televised," about the last 15 years of TV drama, is for sale at Amazon. He can be reached at sepinwall@hitfix.com