Margot Robbie "forgot" she wasn't Tonya Harding and punched her co-star in the head.
The 27-year-old actress threw herself into the role of the disgraced figure skater in 'I, Tonya' and immersed herself so deeply into the part, she got carried away shooting a scene with Sebastian Stan, who played her on-screen lover Jeff Gilooly.
Margot was asked to name her favourite moment during shooting and she explained it was a fight scene that got so intense, director Craig Gillespie ultimately cut it from the finished film.
Speaking at the Toronto Film Festival (TIFF), she said: "Craig kind of on the day was like, 'Just do whatever in the moment,' and we got so carried away that I genuinely forgot that we were on a film set and that I wasn't Tonya and that he wasn't Jeff.
"We got into, like a brawl. He slams my hand into the door. And I ended up storming off down the street, which was, like, the end of set, so I was just on the road in the real world.
"And [Stan was] coming after me, screaming, 'Where are you going?' I think you even said, 'Margot,' and I said, 'I'm going to the hospital because you broke my hand!' And I was so caught up in it and I think I punched you in the side of the head!
"That ended up being my favorite scene because I forgot that I was acting, and nothing makes more exhilarated when I genuinely forget where I am."
Margot had little on-ice experience before she started work on the biopic, and she wishes she'd had more opportunities to skate when she was younger.
She told The Toronto Sun: "It was so much fun.
"But, yes, I was kicking myself that we didn't have ice skating rinks on the Gold Coast. Everyone in Canada is like an amazing skater just by being born here so I felt like I had a lot further to go. I did a lot of training. I did a lot of research."