Ashton Kutcher and Mila Kunis
Ashton Kutcher and Mila Kunis have a 21-month-old daughterGetty

Mila Kunis, who is expecting her second child with husband Ashton Kutcher, revealed that initially she and Kutcher started out as "casual sex buddies". The actress went on to make some interesting revelations about her relationship with the Just Married actor and said that their lives were much like the movies – Friends With Benefits and No Strings Attached.

Speaking with Howard Stern on his SiriusXM radio show on Tuesday, Kunis said that she and Kutcher had kept in touch after becoming friends since That '70s Show. However, it took them quite some time to transit from being casual to serious in their relationship.

"We, oddly, both did a movie called – I did Friends With Benefits, he did a movie called No Strings Attached," Kunis said, adding, "If we just paid attention to these movies, we should know that s**t like this does not work out in real life. Well, we clearly didn't pay attention. We shook hands, we're like, 'let's just have fun!' I mean, literally, we lived out our movies. We literally just had a very open conversation."

According to reports, Kunis fell for her co-star when she met him after a long gap, after he separated from Demi Moore and Kutcher "took (her) breath away". He then invited her for his housewarming party, where they "hooked up".

"Long story short — I didn't leave till the next morning. And that was the first time, ever, that I'd ever slept over when I was single ... at a guy's house," Kunis recalled.

The Black Swan actress continued, "Like, when I was single, I was so adamant about never, as stupid as it sounds, never staying over at a guy's house. I was, like, peacing out, and he was like, 'You're not leaving.' And that was the first time and only time."

Kunis and Kutcher tied the knot in July 2015 and are parents to 21-month-old Wyatt Isabelle. Before advancing with Kunis, the 38-year-old actor was married to Demi Moore. Unfortunately, the marriage failed following a cheating rumour linking Kutcher with Sara Leal. Even Kunis called it quits with her long-time partner Macaulay Culkin.

Although Kunis and Kutcher were initially seeing each other casually, three months later, they decided to make their relationship exclusive. "We started dating with the idea we were both never going to get married," she said. "A year later we were like, 'Tomorrow let's [get married]'," she added.