Based on true events, ‘I, Tonya’ follows American figure skater Tonya Harding, the infamous skater known for her association with a violent attack on her Olympic rival Nancy Kerrigan.

ATLANTA – This is the kind of time-warp whiplash Margot Robbie had to deal with daily in filming the Tonya Harding tragicomedy I, Tonya: Play 23-year-old Tonya arguing with her mother in the afternoon, then put on a wedding dress to get hitched as 19-year-old Tonya that night. 

It’s enough to “make my head hurt,” Robbie laughs. “I am constantly going, ‘Where are we? What’s happened? Are Jeff and I married right now? What bruises should be on my face?’ ”

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In the Golden Globe-nominated biopic (now showing in select cities, including New York, Los Angeles, Boston, Chicago and Atlanta, goes nationwide Friday), Robbie plays Harding from age 15 to her mid-40s, tracking the infamous Olympic hopeful from figure-skating wunderkind with a mean triple axel to national disgrace following the 1994 clubbing attack on Nancy Kerrigan. Through documentary-style “interviews,” the story is told primarily from her point of view as well as the POVs of Harding’s abusive mom, LaVona (Allison Janney), and ex-husband, Jeff Gillooly (Sebastian Stan). 

USA TODAY was on the set of I, Tonya last February and discovered five intriguing things about this year’s most bonkers Oscars contender.

1. Margot Robbie navigated a dizzying number of costume changes.

Ninety, in fact. The actress’ wardrobe, which spanned 1973 to present day, “so cleverly mapped out Tonya’s whole journey,” Robbie says. Designer Jennifer Johnson describes making “a factual timeline” with the clothes, with inspiration coming from grainy VHS footage of Harding’s competitions and old National Enquirer issues purchased on eBay for a wide range of authentic options.

2. But fashion was only the start of her transformation.

Robbie wore padded “fat pants” to add weight in Harding’s heavier times, as well as leg…