The Family Guy actress took part in an AMA session on Reddit – aka Ask Me Anything! – and was totally happy to open up about smooching Natalie in Black Swan.
"When you have a kissing scene in a film it's not something you think about as a kissing thing. You have all these crew around. But she's a lovely kisser, very polite.
"But here's a little known fact: there is one person in the world that both Ashton and I have kissed, and that's Natalie Portman!"
Mila told the thread that Black Swan - set in the world of competitive ballet – had been the most physically demanding job she'd done until new movie Jupiter Ascending.
"We trained for 3 months before production, and I learned how to be in en pointe, and how to be a ballerina. And then for Jupiter, you do maximum amounts of wirework training every day. So for Black Swan, I trained by dancing every day for 3 months, and learning how to get en pointe in 3 months. Ultimately, it was all about learning how to pretend to be a ballerina. And I mimicked my ballet instructor more than anything."
Meanwhile, the movie that Ashton kissed Natalie in was No Strings Attached.
Mila's new film, Jupiter Ascending, co-starring Channing Tatum, is released this week.
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