Jason Reitman's second feature film, Juno, turned out to be the surprise hit of the Telluride Film Festival, before moving on to Toronto. Reitman took time out of his last day at Telluride to sit down and chat about his film, why it works, and why guys just don't want to grow up.

(NOTE: This interview is a discussion of the film that contains spoilers, so if you don't want to know anything about it before you see it, stop reading now.)

Cinematical: Let's talk about how you found the Juno script to begin with and why you wanted to film it.

Jason Reitman: I was fortunate enough that I had Mason Novack (Diablo's manager) found Diablo, and I knew Mason, and so I had a copy of the script as soon as it came out.

Cinematical: And what did you like about the script? What did Diablo do right?

JR: What she did right was this: She took a very tricky piece of material and made interesting decisions at every turn. Every time a character had a line of dialog, every scene, she made the interesting, unexpected decision. Not the usual decision, but that was not precious, but that was honest and real and sometimes very funny. That's what I liked about Thank You for Smoking. That film turns on the world of cigarettes, and Chris Buckley makes those kinds of unusual, hilarious decisions at every turn. Diablo does the same thing, and she's very good at it. span style="FONT-WEIGHT: bold">

Cinematical: Do you look specifically for that in choosing what scripts you want to work with? That angle?

JR: I love the tough stuff. I'm really attracted to movies about tricky subject matter, where it's dealt with in ways that are unexpected, that aren't too dramatic and precious. That's not to say that this movie doesn't have heart, it does have heart, and I think the ending is very moving. That said, it's the fact that she took on tricky material and didn't treat it that way.

Cinematical: I want to talk about the casting. When you first read the script, did you know from the start you wanted Ellen Page?

JR: I'd read the screenplay, had not really pictured anyone, and then saw Hard Candy and I was like, that's the girl.

Cinematical: Did you see her in An American Crime?

JR: No, no, noooooo. I've heard that's raw. I've heard that's really tough to watch. When it came time to cast, I got Michael Cera, JK Simmons, Olivia Thirlby, and I brought them to over, set them in front of a black backdrop shot 45-50 pages, all in one day, and then cut it together, then I showed it to the producers at Fox and said, this is the cast I'd like to have. And they said okay.

Cinematical: Well, that was easy.

JR: Yeah, it really was. It was kind of in lieu of an audition process.

Cinematical: You cast Jennifer Garner, and she's not necessarily the first person I would have thought of, but she gives a fantastic performance.

JR: I'm really proud of what Jennifer did in this film. What she did was very subtle, very complicated. It's through the honesty of her performance that everyone else around her was able to be very funny. The casting of that role was tricky, because it's a woman of a certain age, who you can buy as desperately wanting to be a mother. Someone at you at first find to be a little pushy and unlikeable, and then by the end of the film, it flips, and you've just fallen in love with her. It was very tricky.

Cinematical: Exactly! You start out thinking you know how you feel about those characters, Mark and Vanessa – that she's irritating and uptight, and he's laid back and cool, but then suddenly you realize your feelings have changed.

JR: Right, it flips, and you're like, "Oh my God!" I talked to Jason Bateman and Jennifer Garner about The Queen, and how successful they were at doing that switch. At the start of the film, you're thinking that Tony Blair is wonderful and charming, and the Queen is stodgy and set in her ways, and not open-minded. And then by the end of The Queen, it's switched, and you realize the queen is very aware, and that she has this whole global perspective, and it's Tony Blair who is being very short-sighted. They pulled the rug out from under the audience, and that's what we wanted to do.

By the end, you realize he's incapable of growing up, and when you realize that, and that her desire to be a mother is sweet and sincere, you can't help but fall in love with her. And it's very hard to deal with Jason Bateman's character, because it's a very real thing that a lot of guys do. You know, a lot of people ask me what this movie's about, and it's about the moment at which you realize you want to grow up. Ellen Page's character Juno is given the opportunity to grow up at the age of 16. She could become a mother at the age of 16, to become a grownup and deal with some real shit. And a lot of teenage girls deal with that – teenage girls are growing up faster and faster. And in a weird way, this is a movie about teenage girls growing up too fast, and 30-year-old men who don't want to grow up.

Cinematical: I want to get back to the character of Mark. When I talked to Diablo about the script, she said she felt she didn't write that character quite as negatively as you portrayed him and that you really disliked the character.

JR: I actually liked the character a lot, even though he does very unlikable things. I think the things he does, they're very honest. Look, I'm a guy who became a father throughout the process of the making of this film, and I understand the anxieties he's going through. I went through some of those anxieties, but I came around and embraced the idea of fatherhood, I adore my father. And Mark is a guy who caved into those anxieties, who made the wrong decision.

Cinematical: Do you think he made the wrong decision? Or did he make the right decision, in being honest about who he was and about just not really wanting to grow up?

JR: That's what makes it sophisticated. I think if Mark is too likable, it's not interesting. What makes it interesting is that, perhaps he makes the right decision. Perhaps if he stayed with Vanessa, a few years down the road they'd be getting a divorce and it would have been harder on that family. And perhaps he makes the right decision. It's that complicated, real shit that excites me.

Cinematical: A lot of guys in that late 20s-early 30s demographic seem to really struggle with that in this generation. I mean, guys from my dad's generation, your dad's generation, they had babies in their 20s, they went work and supported their families. What's up with this generation?

JR: Yeah, and I don't know if my perception is skewed because I live in Los Angeles, where in their teenage years – they enter their twenties earlier, but they leave their twenties later. The twenties are kind of extended from 15 to 35 in Los Angeles. And I'm not sure if that's a national epidemic of if that's only in Los Angeles, but a lot of guys are blooming later, they're pushing off the idea of marriage and pregnancy, and they're being allowed to, which makes it worse.

Cinematical: Allowed by whom?

JR: It's somehow become culturally okay. Divorce is epidemic, and somehow in line with all that, the whole concept of what marriage is and when it happens has become more flexible. This is a country that really pushes people to be individualistic, and that might weigh on it.

Cinematical: Do you feel differently about Mark as a character now, as a husband and father, than you would have a few years ago? When you were 25, could you have made this movie?

JR: No, I definitely have a different perspective now. And I think there's something to be said about that, about when people should make certain films and the life experience you need to tell certain stories. I empathize with Mark, but I also empathize with Vanessa – the idea that you're not a whole person until you have a child. And I empathize with Juno, the fears she had about bringing a child into our world. Simply the idea of going through a pregnancy. It would have been nowhere as honest, nowhere as emotional, back then.

Cinematical: I wanted to touch on how you worked with Diablo in making this film. You involved her much more than screenwriters often are able to be involved in films.

JR: You know, sometimes directors are scared of the writers. I like writers, I get along with writers very well, I trust writers. With Thank You for Smoking, I really wanted Chris Buckley to be involved. And with Juno, Diablo's voice was so important to the script. And there were times that I would be like, I need a moment that does this, and she'd bang it out right, she'd write a scene write there on set. Or I'd need to make a decision – this character needs to wear a set of clothes, or listen to certain music, what would it be?

Cinematical: There's a lot of Diablo in Juno.

JR: Absolutely, she is that voice. And there's no way that I could emulate that voice. It's funny, Nick Naylor (from Thank You for Smoking) was a character whose voice I could emulate. With Juno, here was a story that I loved, but that voice is not mine. And I would never think to try to write a Juno scene myself. It's just not my voice.

Cinematical: Did you like working on someone else's script versus doing your own?

JR: It's a little bit different, in that you're carrying someone else's baby into the world, and in a weird sense that it's even more precious. You don't want to fuck it up, you don't want to be that guy who ruined something that was beautiful, who ruined something that someone else created. So you're careful, you want to do it right.