“Oh shit, I can’t believe that just happened!”

From a park bench in La Cañada where this interview is taking place, near the set of a “weed/action comedy” he’s co-written and is co-starring in called The Pineapple Express, Seth Rogen has caught sight of a three-wheeled stroller with a strapped-in toddler as it flips over on a short but steep grassy incline. Suddenly there’s crying, a father quick to comfort his shaken-up son and, from Rogen, instantaneous laughter. Hollywood’s newly anointed comedy star is no chortling wallflower either. When his great deep musical growl of a voice revs up, it can suggest both kingly merriment and the stuff of storybook nightmares.

“That’s terrible,” he says, covering his mouth and shaking his head in shame (but still chuckling). “That’s why I would be a bad father.” Rogen makes sure to let on, though, why this accidental kiddie tumble was particularly amusing: the dad. “He laughed for a split second before he went to pick the kid up.”

A big-but-not-seam-splitting presence in bushy hair and black-rimmed specs, Rogen, who turned 25 in April, has a bearish affability in person that seems ideally suited to humor both gonzo and vulnerable. “Good comedy doesn’t have to be a comedy idea,” says Rogen, who uses the two white-hot-buzz movies he’s got out this summer — the Judd Apatow–directed relationship flick Knocked Up and Superbad, a beer/bongs/babes high-school freakout Rogen co-wrote — as examples. “If someone describes a movie about how a couple gets pregnant from a one-night stand and they’re forced to see if they’re mature enough to raise a baby, that’s not necessarily a hilarious idea,” he says of the dilemma faced by his Knocked Up character, a toke-addled aspiring Web-porn entrepreneur. “And if you said Superbad was a movie about two best friends going to different schools and having trouble coming to terms with that, it doesn’t scream comedy. But more than anything, that’s what Judd’s taught me about writing. Find the emotional story, and all the humor will come later.”

If Apatow schooled Rogen, whom he’s known since their days on the NBC series Freaks and Geeks, in the ways of underlying drama, then Rogen has just as assuredly been Apatow’s filth-humor muse on Knocked Up and their previous film, The 40-Year-Old Virgin. The new movie spares nothing in the way of profane roommates-without-responsibilities gags, but Rogen isn’t worried about such fretted-over Hollywood notions as character likability. There are trade-offs, anyway. A smiling Harold Ramis plays your dad? That buys 30 asshole moments. “My characters come from a good place,” he says. “I can make a million dick jokes. As long as I don’t bail on the pregnant chick, my guy’s a good guy.”

Of course, the va-va-voom factor of Rogen’s Knocked Up co-star, Katherine Heigl, will raise quizzical eyebrows among moviegoers all too accustomed to the I’m-with-hottie imbalance of male-centered comedies. But Rogen recalls the moment he knew Heigl was the right bombshell mother-to-be. “The audition scene was us arguing in a car and she kicks me out, and she fuckin’ just unloaded on me,” he says, a tinge of awe entering his voice. “It was hilarious! And I remember thinking, I can be a lot funnier with her. Put me next to a 90-pound, 5-foot-3 actress and I’m fucking Giant Jew Screaming. It just seems horrifying all of a sudden. But [with Heigl] I can scream at her, call her a fuckin’ idiot, and it doesn’t seem nearly as mean, because she’s strong, tall, loud, not afraid to say shit, and can take care of herself. I really feel like they’re not letting her do 1 percent of what she’s able to do on Grey’s Anatomy.”

Wait. Seth Rogen watches Grey’s Anatomy? The guy who ad-libbed Virgin’s towel-snapping “You know how I know you’re gay?” bit into movie-comedy immortality? “It’s because of my girlfriend,” he qualifies. “I feel like there needs to be the equivalent of that seating area by the dressing rooms in department stores. A little football game running in the corner of the screen.”

As for what was required to distract a hey-it’s-just-me kind of actor from the nervousness of pretend-fucking a cover-girl babe like Heigl, Rogen is grateful that those scenes — which include a position-fumbling exercise in pregnant-sex etiquette — left room for him to be funny. “You’re wearing little flesh-colored underwear and you’re effectively dry-humping someone, and it’s very weird,” he says. “It’s the exact opposite of real sex, because I was trying not to get an erection instead of trying to maintain one.”

If sex kicks off the plot of Knocked Up, for the horndog teen geeks of Superbad (which could just as easily be called The 17-Year-Old Virgins), it’s a mystery goal that inspires crazy schemes and profane discourses that are paradoxically — and hilariously — worldly and clueless. The film’s detour-heavy shenanigans cover a wild night in which two joined-at-the-hip high school seniors (Michael Cera and Jonah Hill) make herculean efforts to provide the alcohol for a house party where they hope their long nightmare of nookielessness will finally end. “It’s funny, the Internet and my sexual development really could not have timed out more precisely,” says Rogen of the puberty struggles that informed Superbad. “It’s terrible for a kid: The second you want as much porn as you can take in is literally the day that’s able to happen. It was crazy.”

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Rogen says he’s chilled out since, now that he has a girlfriend of two years. “It’s changed me,” he acknowledges. “Judd’s wife [actress Leslie Mann, who plays Heigl’s sister in Knocked Up] will constantly remind me how much she disliked me before, and how much she likes me now.”

He’s also not worried about how billboards with his face on them and possible stardom will alter him. “Will it affect my ability to play Grand Theft Auto? I don’t go out that much.”

Growing up in rainy Vancouver, Canada, Rogen was probably destined to be an indoor type. Huddled with bar mitzvah–class friend (and now writing/producing partner) Evan Goldberg during non-school hours dreaming up Superbad, or working on student-life jokes and boob-touching riffs for his standup act, the grades-challenged Rogen had the full support of his “hippy-dippy left-wing kind of Zionist socialist” parents, as he affectionately calls them. “Evan’s parents would tell us we were wasting our time, and my parents would be buying me Final Draft and doing anything they could to get me into clubs to do standup. Standup was my version of a paper route.”

At 16, Rogen got an agent in hopes of nabbing commercials or bit parts in American TV shows shooting in Vancouver. Right off the bat, he landed an L.A. series: Freaks and Geeks. Rogen’s first-ever appearance on film is the pilot of that critically praised but network-troubled show about exquisite adolescent awkwardness, which also describes the untrained teen actor who felt out of his element. “I remember meeting [Freaks co-stars] James Franco and Linda Cardellini and thinking, ‘Wow, these people actually think about this and have opinions as to how to execute this.’ I remember not even thinking about whether it was a good show or not. I was just so amazed I was cast in something.”

But even then, Freaks show-runner Apatow saw in Rogen the mixture of sweetness and coarse wit that could carry a movie. The two developed a symbiotic friendship and collaboration in which responsibility bestowed by Apatow spurred unexpected ambition in Rogen. Hired as a writer for Apatow’s subsequent TV series Undeclared, Rogen made sure he was the one reading on videotape with every auditioning actor, which got him noticed by Fox executives and eventually cast on the show. Four years later, when Apatow got the green light to direct The 40-Year-Old Virgin at Universal, Rogen — with whom Apatow had been consulting on the script — aggressively lobbied for co-producer status (that is to say, on-set joke writer/“Is it funny?” auditor) and an onscreen role bigger than Occasional Wisecrack Guy.

For Rogen, who had gone through a vulnerable patch of failed auditions after Undeclared was canceled, speaking up was tough. “I remember psyching up to it, because in the past I’ve had trouble with motivation slash work ethic. Four years of unemployment will definitely knock that out of you. And Judd said instantly, ‘Okay, sure, why not?’ It almost seemed like he was waiting for me to say it.”

Apatow, however, calls Rogen’s fallow years “the path of a great comic,” in that they taught him patient dedication to seizing the right moment. “The most interesting people don’t fit into the job descriptions out there for actors,” says Apatow. “I just kept saying to him, ‘Don’t do crappy movies. Keep your IMDB page looking good.’ And now people are rooting for him to succeed because he doesn’t have a trail of awful performances that he took to pay the rent. The same reason he was good at being unemployed is why he’ll be good at being successful.”

With Knocked Up now in theaters and two movies yet to be released, comedy’s new minimogul jokes that, for all anyone knows, he could be box-office poison. But as long as there are dads laughing at their kids’ pratfalls, and as long as Rogen gets to keep making his dirty comedies with heart and stoner action movies together with his friends (including Freaks and Geeks alums Jason Segel and Martin Starr and Undeclared’s Jay Baruchel, who play Rogen’s roommates in Knocked Up), then how much better could life get? “I gave Ben Stiller and Owen Wilson so much shit behind their backs for constantly doing movies together, and now I’m in movies with the same people all the fucking time! I’m like, ‘I get it now, fuck it, I was an asshole! I take it back!’ Now, I can’t think of enough ideas for us all to do. I want to get everyone together! We should just remake Cannonball Run!”

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