Zach Braff, Jacinda Barrett and Rachel Bilson on their new film

A love triangle can be a tricky thing to handle. That's what Zach Braff, Jacinda Barrett, and Rachel Bilson have to do in their new film, The Last Kiss.

Zack and Jacinda are engaged, and expecting their first child. At a friends wedding, Zach meets Rachel, a college chick with nothing by innocence. Not happy with the direction his life is moving in, Zach decides to begin a secret relationship with Rachel. When the truth comes out, all hell breaks loose between Zach and Jacinda; their impending marriage and relationship is put in jeopardy.

It was a role Jacinda had the chance to really show her acting chops, and was an emotional roller coaster for her character. "It's impossible to just stay in that all day long, including your lunch hour, including a hour while they set up the lights; it just doesn't do you any good. At a certain point it if you keep doing that, it dissipates, the emotion leaves you altogether. So I find for me what is the best sometimes, depending on the scene - like the scene with Blythe where I'm on the floor and she's leaning over me and talking to me and I was crying, they just used music before every take. But then that confrontation scene with Zach, we shot that all day for 12 hours, and I just would go into it and then go out of it and start laughing at the end of it. Because laughter's often the other side of that extreme tears and vulnerability, it's sort of like ridiculousness at what you're going through, so I would forget about it, we would joke around and then we would start up again. That's how we got through that."

That scene for Zach was, in a way, a realization into real human characteristics. "One of the reasons I wanted to do this movie was it was so refreshing, it was real. It was like a human being that f*cks up, that makes mistakes, that does a dumb thing and don't we all. Don't we all have things that we wake up the next day and go, 'Oh, I'm such an idiot.' You read so much crap and then I read this and I was just so drawn to it. There'll be some people that'll come out of the movie hating me and some people will come out the movie going, 'G-d, I've been there, I can relate to what he went through.' And I think there'll be people that will be shocked at how human the characters in this movie are."

And Rachel, being the newcomer to the big screen, had to be the 'other woman.' "It's always hard, cause there's a lot of things that go into playing that; you never want to be the 'bad guy' really. It shows her in a different light; she's very likable in some ways, a little more forgivable, I think in a way, which helps because you don't always want that big of a 'bad guy' and you hate the character by the end of the movie and you don't see the point that was trying to be made."

Rachel and Zach also had a very steamy love scene, something Zach made sure looked natural. "I think what's great about it is it would have been so much easier to make her a dumb ditz. One of the things I loved about Paul Haggis's screenplay was that he made the conscious choice to make her charming and likeable and adorable and sexy, and that makes it more challenging for him and the audience. Now, I do think that we see that she's a baby; she's young and they're not going to have that much to talk about after they get out of the frat party. And I think even looks wise, you almost think wow, Rachel in 10 years will look like Jacinda. So I don't think they'll be - you're right. I think it was brave of Tony (Goldwyn) and Paul Haggis to leave everything up in the air because these things don't get wrapped up in a nice five minutes."

For the female perspective, "It was my first time and I was happy it was with Zach because he was very respectful, and made me feel very comfortable. You just do it and it's a bigger deal to watch or think about, then it was to actually deal with it, I think. For some reason, there are these people you just kind of see and think they're interesting. And then you talk to them and it's about it, because they're charming and funny. I think she sees him from across, and she's drawn to him; I think it's genuinely him and not just some guy she's looking for."

Jacinda and Zach do have good times together, even involving Zach's gas problem. "He did it for real a couple of times I think; he has a little bit of talent that way, he's an on-cue kind of guy, it's impressive. I don't know if we had a sound effect; I think a sound effect would have been too funny to hear a random fart coming from the other room, so I don't think we had that. But it was a funny moment for us every time we'd be shooting it, because even in real life that stuff happens, it's both gross if someone does it on you and at the same time hilarious. That was a fun day.

Blythe Danner and Tom Wilkinson play Jacinda's parents in The Last Kiss. Having that legendary star power on the set was incredible for the cast. Zach fondly remembered the interactions he had with the two. "Blythe, I think could get nominated for her work in this movie; I just couldn't take my eyes off her, I think she's just fantastic. I had that scene with Tom where I really got to act with him. There's that really awful analogy of playing tennis with someone that's better than you but I really do feel - I really felt like that. He's so good and so present and so there. Every once in a while as an actor you have these moments where you're really in the scene and for split seconds at a time you forget about the camera and you forget about the boom mic and you're really listening to this person, and then it comes back and you're on set again. But with Tom, it was like I'd have these long, full seconds where it was like I was listening to him and I was there, and it was just really powerful. I think that shows in the scene. It was really like an older guy giving a younger guy life advice."

Jacinda had actually worked with Tom before on a previous film, but it was a very different feel and tone. However, Tom remained the same; "He just has this incredible strength and is the calm inside the storm in this character. This stoicism that was such a different quality than what Blythe brought, which was this more frenetic, emotional and very mercurial in the way she would be happy one minute and then upset in the next. In that scene in the dining room, especially when we first tell them we're pregnant, you see all those qualities in her. And so it was really fun to watch how they each approached their characters. Blythe would literally put a hand on my face, and she has such a mother's touch it would get me emotional. It was a great experience working with both of them, and they're clearly the old pros in the movie, they've been doing it longer than any of us."

But we couldn't let an interview with Rachel go by without asking her about The O.C.. She said it's very different without Mischa Barton around. "It was weird, especially the first day because her dressing room is empty, she's not there, and she's definitely a force. And it was so nice having her in the mornings to liven up the trailer. But, it's just a job really, and we're just doing our jobs the best we can. On the show, everyone's dealing with the death of Marissa Cooper, and that's what we're doing right now. We'll see what happens from there; they always come up with something."

But you can see Rachel, Zach, and Jacinda in The Last Kiss; it opens in theaters September 15th, rated R.