'Knocked Up' Spin-Off News Surprised Seth Rogen

'I just read about it just like everybody else,' original star tells MTV News. 'I was like, 'Oh man, it looks like it's really happening.' '

Much like "16 and Pregnant" gave birth to "Teen Mom," it seemed as though if Judd Apatow were ever to return to the world of "Knocked Up," his hit 2007 comedy, the writer/director would continue the story with more about Seth Rogen and Katherine Heigl's characters and the child they had together.

But that's not what's happening — not least of all because of the messy public backbiting between Apatow and Heigl over her character, Alison. Instead, Apatow is pushing forward with an extension of that world featuring Alison's sister, Debbie (Leslie Mann), and brother-in-law, Pete (Paul Rudd). The film will apparently tell a story separate from the one told in "Knocked Up," a story that simply focuses on Debbie and Pete's troubled marriage.

Still, the question remains: Will Heigl or Rogen pop up at any point in the new film? MTV News put that very question to Rogen when we caught up with him while he was promoting "Green Hornet."

"I don't know," he admitted.

Rogen went on to explain that he had some knowledge that Apatow was working on "Knocked Up"-related material, but didn't know if a project was locked in or if there's a part in the script for him.

"[Judd] mentioned it to me off-handedly a year ago, and then I just read about it just like everybody else," Rogen explained. "I was like, 'Oh man, it looks like it's really happening.'

"So, I don't know," he added. "I'm going to call him today and see what the deal is."

Check out everything we've got on "Knocked Up."

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