Sean's Man-on-Man Smooch

In the new Gus Van Sant-directed film, Milk, Sean Penn shares a steamy kiss with co-star Mark Martinez, who says the Oscar-winner let the lip-lock go on a little longer than expected.

"I'm performing, and [Penn] comes onto the dance floor," Mark tells E!. "He grabs me, and he just slaps the biggest kiss on me...It felt like the kiss was forever. I'm like, is he going to stop? I had to close my eyes, I couldn't believe it."

In the film, Martinez plays the late cross-dressing disco singer Sylvester. In one scene, the actor, dressed in a purple, blue and silver kimono with a matching turban and black bell bottoms, performs Sylvester's 1978 hit, "You Make Me Feel (Mighty Real)"

"All of a sudden, Sean's pointing at me and he's talking to the assistant director," Martinez explains. "The assistant director comes up to me and says, 'Just to let you know, you are now going to break up Sean and [co-star] James Franco's conversation. You're going to grab Sean, and Sean's going to be really excited, and he's going to kiss you.'"