The star of Knocked Up talks about his character, and getting to make out with Katherine Heigl.

Actor/writer/comedian Seth Rogen stars in this weekend's big opening movie, Knocked Up, director Judd Apatow's follow-up to the splash success The 40-Year-Old Virgin. Knocked Up is a comedy about a slacker named (Rogen) and an entertainment journalist (Katherine Heigl), who make an unlikely couple when they have to deal with an unexpected pregnancy.

Rogen got his start in show business by doing stand-up comedy in a Vancouver lesbian club when he was just 13 years old, and first hooked up with Apatow when Apatow cast him in the ill-fated Freaks and Geeks (it cancelled after one season despite a strong cult following). Over the years, Rogen has become an integral part in Apatow's comedy crew, which also features actors Paul Rudd, Steve Carell, and Leslie Mann--Apatow's wife, amongst others.

Rogen had a supporting role as Cal, one of Steve Carell's character's friends, in The 40-Year-Old Virgin, which he also co-produced. He executive produced Knocked Up. "My duties were being near Judd at all times," explains Rogen. "I tell him, 'I'm just going to give you my opinion until you tell me to shut up.'"

As someone more apt to take his shirt off for a laugh than to steam up the audiences' glasses, Rogen seems an unlikely choice for a romantic leading man. But that is precisely what this movie called for. "It's a strange concept, I guess, that romances are something that people want to see me do on film," says the typically humble Rogen. "But I had fun."

Fun--except for all those (albeit comedic) sex scenes he had to shoot with Heigl. "It's really kind of nerve-wracking," says Rogen. "You're essentially--you're dry humping. I don't know if you can say that or not, but I'll say it. You're dry humping a girl who you don't know very well, and I was just afraid I was going to sweat on her. That was my concern--that I was going to drip a big gob of sweat on her head."

He adds: "If I was 18-years-old, it would have been literally as far as I've ever been with a girl."

A young slovenly stoner who lives with no real source of income, Rogen's character, Ben Stone, is a rather unlikely romantic hero. "I think almost any guy is redeemable, if you haven't don’t something truly terrible," he explains. "I think more than anything our movies have a very simple message, which is to try to be a good guy or girl, just do the right thing, as Spike Lee says."

And that mentality explains why Rogen and Apatow can get away with their particularly bawdy brand of humor. "You can kind of have people say all the filthy, despicable things you want and have them do stupid things, but as long as you get that character's trying to be a good person throughout it all, that's kind of all I need to latch onto," he explains. "It's simple, but I think, emotionally speaking, it's true to my experience with people. If you meet someone, everyone has their shortcomings. But as long as you see they're generally trying to do well by others, then they're very' redeemable, I find."

Knocked Up, starring Seth Rogen and Katherine Heigl, opens in theaters nationwide on Friday, June 1.

Check out ReelzChannel.com's Knocked Up page for clips from the movie and more!