Katherine Heigl felt "uncomfortable" around Ashton Kutcher because she had seen what he looks like when he orgasms.

The actress co-stars in new movie 'Killers' with Ashton and during shooting the actor gave Katherine a copy of his indie film 'Spread', in which he is involved in many sex scenes, leaving her feeling highly embarrassed.

She told E!: "He gave me the movie to watch. I watched it one day during lunch, but when I went back to work, I was like, 'I don't know if I could look at you right now. I know you far too intimately and I'm really uncomfortable. I've seen your O-face!' "

However, Katherine soon got over her embarrassment and loved working with the Hollywood heartthrob - who is married to Demi Moore - especially during the kissing scenes.

She said: "He is stupid hot. It's ridiculous. Even his hands are beautiful. His kissing is unbelievable. Could you imagine if he sucked? I would have slapped him."

In the romantic comedy, Katherine - who raises an adopted daughter, Naleigh, with husband Josh Kelley - and Ashton play two lovers who are hunted down by assassins and the pair get intimate in many scenes.