Ashton Kutcher originally wanted to set Mila Kunis up with his friend.

She said: We'd always kept in touch but I never thought of him romantically. I was at an awards show and I see this guy and I see his back and he's really tall. I was like, 'Who's that guy?' Then he just turns around and it was literally like if we were in a movie, the music would start playing and the violins would go...I think for the first time ever he took my breath away...I was like f**k, he's good looking.

"He had planned to set me up with his friend. Long story short, I didn't leave until the next morning. It was the first time I had stayed over at a guy's house when I was single but he didn't want me to leave."

However, they initially decided on a casual arrangement, similar to her movie 'Friends With Benefits' and 38-year-old Ashton’s 'No Strings Attached'.

She told Sirius XM: "I don't know if I should tell this story, I could get in trouble for it. We were in similar movies and we should have paid attention to them because this doesn't work in real life. We clearly didn't pay attention and we shook hands on it and said we would just have fun. We literally lived out our movies."

Mila admitted that neither of them planned to get married, as she had previously been in a long-term relationship with Macaulay Culkin and Ashton was divorced from Demi Moore.

She said: "We started dating with the idea we both were never going to get married. He had just got out of a marriage and I had gotten out of a relationship. We shook hands on it and life was great. But we were in agreement that it was just fun. And three months later, I was like, 'this isn't just fun anymore'.

"And then a year later we wanted to get married. I think it took everyone by surprise."

The couple are now expecting their second child together.