What happens when two high school lovers are reunited by the reappearance of the daughter they'd given up for adoption turns up? That was the conceit of the first season of the CW's "Life Unexpected," which premiered this Spring and garnered a strong enough amount of viewers to be granted a second season. As that second year kicks off tonight, teen daughter Lux (Britt Robertson) continues to go through teenage growing pains (and a potential fling with an authority figure at school!) while her mother, Cate (Shiri Appleby) contends for lingering feelings for Lux's father, Baze (Kristoffer Polaha) on the heels of her marriage to Ryan (Kerr Smith). As if that wasn't enough to keep track of, creator Liz Tigelaar told our Jim Halterman last week how she incorporated new faces and how a crossover with long-running series "One Tree Hill" was coordinated (and who crosses over).

Jim Halterman: Once you found out the show had been picked up, how did you come up with the stories you wanted to tell?

Liz Tigelaar: In order to get the pickup, I had to go in and pitch the whole second season with a really extensive pitch. I pretty much spent all of hiatus working on that because I knew that would make the difference to show the network where the show could go. I was instructed to open the show, make it bigger, more characters; certain mandates. I think for me there was a lot of 'How do I give the network the show they want and still stay true to the type of show that it is and the stories I'm compelled to tell.'

During the first few months of being back and doing the premiere, I was so scared of it turning into a different show and not knowing if I trusted the notes or the process. When it was finally said and done, I felt 'I think it works.' When I saw that first cut, I said 'I understand now! I get how to broaden it out and keep the same heart!' A lot of people have said it feels like a better version of the same show.

JH: You definitely have a lot of new faces right off the bat. How did you go about incorporating them without shaking things up too much?

LT: I think the big question of the first season was its own little arc that needed to be told to kick off the series. We have to see them all get to know each other and invest in each other and not just because they had to but because they wanted to and they had to become a family. Now that they are a family it's not so much about that conflict - not that all families don't have conflict but it's not like anything is going to tear them apart anymore. The four of them are a family so now it's how do we introduce new conflict. With Cate and Ryan Baze had been the main source of tension for so long so we tried to introduce characters that would highlight new and different conflicts.

I think Cate and Ryan certainly have that in the addition of Kelly, played by Amy Price-Francis at the workplace. With Lux, I really wanted to explore stories with her - she has two parents, she was adopted, she doesn't have a reason anymore to not feel normal on the outside but what keeps her from dating the quarterback or from seeing herself from being able to be a normal high school kid? What kind of relationship can exemplify not feeling normal or feeling that you're above the rules?

JH: What are we going to see with Baze now that Cate and Ryan are married?

LT: With Baze, this is a guy who just wants to be seen as a grown-up so badly. We're introducing Emma Caulfield in episode 2 to be a foil for him and pull him towards the grown-up world a little bit. She's so good it's crazy! We wanted to cast her forever, we wrote the part for her, we named the character Emma. [Laughs.] We could not have been more obvious! It's really fun and they have really great chemistry and you pretty much can see it in the dailies.

JH: The bar also burns down in the season premiere. Are we losing that location altogether?

LT: The bar is going to be a burned-out set for a while but eventually it's going to be rebuilt. Baze will move away from it for a while but he'll move back to it eventually. It still remains one of our sets but it serves as a nice metaphor for where they are in the first thirteen [episodes]. I think whenever we have scenes in the burned out bar it's kind of a metaphor for where they are.

JH: The One Tree Hill crossover would be fun but why not a 'Vampire Diaries' crossover? [Laughs.]

LT: Oh my God, that would be amazing! I don't know how we'd do it but I would be so happy to work with 'The Vampire Diaries!' That said, the crossover with 'One Tree Hill' is amazing! I think I was skeptical at first how it all would work.

JH: How did the crossover work?

LT: I didn't understand who writes it and all that stuff but it turned out I did! It turned out to be perfect because Mark [Schwahn] was so great and easy to work with us. They gave us a lot of leeway in terms of what we would do. It turns out that the character of Cate and ['One Tree Hill's] Hayley (Bethany Joy Galeotti) were both dorky valedictorians that got pregnant by high school athletes named Nate or Nathan!

So, basically what happens is that Mia (Kate Vogele) from 'One Tree Hill' comes over to participate in K100's radio sponsored music festival and Ryan and Cate are two of the people doing the festival. Hayley, as Mia's producer, comes with her and they both end up performing. We also have all these amazing bands perform and Sarah McLachlan.

JH: As we go into season two, do you think viewers who didn't watch the first season can easily jump in?

LT: I do. I don't think there's anything that's that complicated to figure out. It's a pretty easy concept. If you can jump in on season two of 'Everwood' or 'Dawson's Creek' or even 'Felicity' then I don't think this would be any more challenging. Even with 'Vampire Diaries' there is a mythology but I think you can even jump into that.

The second season premiere of "Life Unexpected" airs tonight on the CW at 9/8c right after the season premiere of "One Tree Hill."