Matt Damon: Kissing Michael Douglas Is Like Kissing Catherine Zeta-Jones

Michael Douglas (left) and Matt Damon

Juan Rico/Fame, Hot Shots Worldwide/Splash News Online

He's done the math, and Matt Damon sees hidden benefits to kissing Michael Douglas in their upcoming biopic about the late, flamboyant pianist, Liberace.

"I never thought I would get to kiss Michael Douglas," Damon, who will play the boyfriend of Douglas's Liberace, told PEOPLE Tuesday at the premiere of a different film, the documentary His Way, in Los Angeles.

"I kind of think of it in algebra terms, back to my high-school days," added Damon. "It's like the transitive property ? by kissing Michael Douglas, I am making out with Catherine."

He's referring, of course, to Douglas's wife, Catherine Zeta-Jones. Damon has worked with the actress in the past, on Ocean's Twelve, but Brad Pitt was the romantic lead in that one, which left Damon ? PEOPLE's Sexiest Man Alive 2007 ? a bit frustrated.

"I was actually kind of upset that I never got to kiss Catherine," the father of four daughters deadpans, "but now I get to kiss Michael. I thought it would have been better if I could have at least kissed them both."

Damon, 40, says he and Douglas, 66 ? who is returning to work after battling cancer ? are both excited about the film. "They're two really great roles, and we're really looking forward to it," Damon says.

As for the kiss, they'll have lots of practice. "There's scripted that there's actually more than one," he previews.

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