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Seth Rogen: Ghostbuster? Those who have read rumors about Rogen being involved in the new "Ghostbusters 3" project should promptly dismiss them.

"It's hard to imagine that would be good, isn't it? I mean, just as a movie fan I am the first guy to be skeptical of that. It sounds like a terrible idea when you first hear it," Rogen says. "I mean, that would have to be one mother [expletive] good script."

Considering how busy Rogen is these days, it's hard to imagine how he'd fit it into his schedule anyway. His latest comedy, and one of his best, "Zack and Miri Make a Porno," hits theaters on Halloween. Written and directed by Kevin Smith, one of Rogen's direct influences, this R-rated spin on a romantic comedy finds two longtime friends deciding to make an adult film in order to pay off their debts. Things get complicated when Zack (Rogen) and Miri (Elizabeth Banks) realize they may have more than fraternal feelings for one another. Considering the title, the film is surprisingly tame in what it shows, but Rogen still ended up almost baring it all. Although he didn't have to go full frontal like his buddy Jason Segel in "Forgetting Sarah Marshall."

"Luckily or not, we didn't have to go too far. I didn't know what Kevin expected of us," Rogen says. "I didn't really care. I was ready for anything. I have no shame about it. It's fine."

Currently shooting the dramedy "Funny People" alongside Adam Sandler for mentor Judd Apatow ("Knocked Up"), Rogen says working with Smith was a strikingly different experience. He reveals that Apatow goes into a movie not always knowing what he wants in a scene. He may have specific plot points, but is unclear of how it should be said and lives for the improvisational skills of his actors. Smith, on the other hand, sticks to the script more and has a clear plan of attack.

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"They both have their merits. They both have things that make them so difficult. But it was really interesting to go into this totally other world, and I really enjoyed it," Rogen says. "I didn't have to think as much. That was a lot nicer. Just going in every day not having to come up with 13 hours of [expletive], that was nice."

Hard at work getting in shape for his upcoming role as the crime-fighting hero the Green Hornet, Rogen is notably thinner today than when he shot "Zack" this past winter. As for his personal trainer, Rogen jokes, "I go there real early in the morning. I'm barely awake and he tells me what to do and I go home to sleep and it's like it never even happened."

And it turns out that his weight loss isn't studio-mandated. In fact, Rogen says, "Honestly, they didn't care at all. I mean, I actually see [Sony Pictures Co-Chairman] Amy Pascal, I run into her on the lot, and she's like, 'You're too thin! You've gone too far! Stop it!' But, yeah, they don't care at all."

"Hornet" won't begin production until May, but Rogen is thrilled to be working with legendary Hong Kong filmmaker Stephen Chow, who is making his first Hollywood film and will also play the hero's sidekick, Kato. Rogen elaborates, "Every time we're in a room with him we're like, 'How the [expletive] did this happen? We got him! We actually got him!' And it's exciting because a lot of people want to work with him, so as we hire our production designer and cinematographer we're getting to choose from very good people because, and we didn't know this, apparently it's as exciting to everyone else as it was to us that Stephen is making a movie in America."

Amen to that.

"Zack and Miri Make a Porno" opens nationwide on Oct. 31.