Allison Janney had seriously trained to become a figure skater throughout her childhood and adolescence. However, when she was 17, she accidentally walked into a sliding glass door and gravely injured her right leg. In 2014, during an interview on "Fresh Air," Janney told interviewer Terry Gross that her leg came close to being amputated. "I lost like three-quarters of my blood. I lost an artery and cut tendon....I was in the hospital for like seven--seven, eight weeks. I missed my first year of college. You know, and after that, of course, I didn't really--I didn't skate for a very long time."
To prevent damaging her hair, Margot Robbie wears wigs as Tonya Harding. Surprisingly, the hair team used beer to achieve the "crunchy" permed look when regular hair products didn't produce the desired result.
Not being a 'bird' person in particular, Allison Janney had some difficulty adapting to having one perched on her shoulder for so many of her scenes, so the production had to 'audition' three different birds before settling on one they nicknamed "Little Man," the least hyperactive of the lot.
Although Margot Robbie trained for the role, she wouldn't be able to do Tonya's triple axel as very few people in the world are able to and at least two of them were training for the Olympics. The choreography was done and the scenes were completed with the help of visual effects and CGI.
Nancy Kerrigan stated in interviews relating to her Dancing with the Stars (2005) appearance that she wouldn't be seeing the movie despite not knowing how much of it would feature her, saying "I already lived through that."
Writer Steven Rogers, a long-time friend of Allison Janney, wrote the role of LaVona Golden with Janney in mind. He'd written several roles for Janney in the past, but other actresses ended up getting those parts. She later thanked Rogers in her acceptance speech for the Best Supporting Actress award at the 75th Golden Globes for convincing her to take the part.