"There's an explosive surprise," says Black of a bedroom scene with Marsden
Credit: Angela Weiss/Getty

Jack Black stars opposite James Marsden in the upcoming high school reunion comedy The D Train, but it wasn’t all laughs on set – things got hot and heavy for at least one scene!

In the film – due Friday – Black’s character has his heart set on getting Marsden’s, a Hollywood actor, to return for the reunion.

“The question is: How far will I go to get him to come … to the reunion?” quips Black, 45.

The actor won’t spill on exactly what goes down between the pair, but he promises, with a laugh, “there’s an explosive surprise waiting for you.”

As for what it’s like joining Marsden in the bedroom?

“You know, I felt a little insecure because he’s a real physical specimen, you know?” says Black. “And never has my lack of muscular tone been so painfully on display.”

For more on Jack Black, pick up the latest issue of PEOPLE, on newsstands Friday