Relationship with Ashton Kutcher started as casual sex then we fell inlove - Mila Kunis

Mila Kunis and Ashton Kutcher are now married and expecting baby no. 2, but their love story is a little weird and sweet. The two met in 1998 as co-stars on the hit sitcom "That '70s Show" where they played onscreen boyfriend and girlfriend. But because of their 5-year age difference, dating wasn't possible.

 "I'm 14, he's 19," Mila Kunis told Howard Stern last week of their first season together and how they eventually had to kiss on camera. "I don't know who it's weirder for."

"I never looked at him as somebody that was good looking, I never looked at him as somebody that wasn't," Mila said.

Their relationship remained platonic and they remained in touch with none of them thinking of dating until 2012 when Ashton got divorced from Demi Moore.

Their relationship took a romantic turn after Mila saw Ashton from behind at a party.

"I see this guy and I see his back and he's really tall," Mila recalled. "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---, he's good looking."

Things started to heat up after Ashton invited Mila to another party at his home... to meet a date! When Ashton saw her and the friend she arrived with, he refused to introduce her to 'the date'. And after the party, asked her to spend the night at his house.

"Long story short, I didn't leave until the next morning," she revealed. "It was the first time I ever slept over while I was single."

After the night together, they called each other casually to talk but weren't thinking of a relationship.

Mila said they agreed to "live out" their movies. They starred in similar films --Mila in "Friends With Benefits" and Ashton in "No Strings Attached" -- where the characters had casual sex but tried to remain friends.

"If we just paid attention to these movies, we should know that sh-- like this does not work out in real life," Kunis joked. "We clearly didn't pay attention and we shook hands and said, 'Let's just have fun.' Literally, we lived out our movies."

"So then we ended up having a lot of talks about how this is a huge mistake," she added. "We both were in agreement, 'This is just fun.' Three months later, I was like, 'This isn't fun anymore!' We didn't want to see other people"

They became exclusive and the rest in history.

"I think we both had to go through a lot in our lives to become the people that we were because we would never be together based on the people that we used to be, ever," Mila told Howard.