Lee, 53, was surprised how ripped director Niki Caro and trainer Bojan Mladenovic wanted to make his Böri Khan for the live-action remake now streaming on Disney+ (as a $30 premium add-on).
"Bojan said to me, 'Hey, can we make an agreement? I think you can get down to 4% body fat,' " Lee recalls with a laugh, speaking by telephone from his Hawaiian home. "I said, 'Holy cow! You know I'm in my 50s.' But he said age doesn't matter. We shook hands. Deal. That was the end of the old me."
"Then I was tortured to death every day," adds Lee. "I was walking crooked for months."
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Caro was going in a slightly different direction from the 1998 animated original "Mulan," which had hulking villain Shan Yu, when casting 5-foot-9 Lee.
"If they wanted that Shan Yu-type imposing, they would have gotten another actor," says Lee. "They wanted me to be really lean and stripped down. A sinewy, snaky character."
Khan is a ruthless tribal leader seeking revenge for his father's death at the hands of the Chinese Emperor (Jet Li) while fighting for his people's land and culture. Holding an uneasy alliance with the witch Xian Lang (Gong Li), the flowing-haired Khan eventually faces off with the titular warrior Mulan (Yifei Liu).
Caro admits she almost didn't cast the American actor of Chinese and Hawaiian descent due to his sweet demeanor.
"Jason's such a gentle man. I needed a shredded killer," says Caro. "But he's such a good actor and I knew he'd take his preparation very seriously."
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Lee already came packing the beard and mustache – "I just grew it all out," he says – while the flowing Khan locks were a noticeably heavy hair weave. Khan's heavily scarred appearance started with an actual scar on Lee's chest from an injury he received while filming a movie in Kazakhstan that got infected and is impressively permanently raised.
"It's pretty awesome, and they enhanced it. They loved it so much they used it as a template for the others," says Lee, who spent two hours in the makeup chair for his facial scars.
He worked on his scowl continually, even on the street. The actor knew he was hitting on villain gold by the expression on passersby's faces.
"I'd be walking and testing my scowl, going, 'What if I did something like this?' says Lee. "I'd look up and see people looking like, 'Oh, my God, he's going to tear me out.' "
The Khan body was the hardest part, requiring double workout sessions over two-and-a-half months marshaled by Mladenovic. Warm-up alone was a half-hour of exhausting bear crawls. Then the real workouts began. "I mean, that was intense," says Lee, who would drag himself home to his wife of 12 years, Diana Chan. "I told my wife, 'I have a little bit of an inkling of what labor feels like.' "
The diet was just as rigorous. Lee would finish his typical dinner of 10 egg whites with a banana for dessert, and Diana would bring home aromatic Chinese food, which he couldn't touch.
"It was like, 'You're torturing me!' But she couldn't believe I was eating like I was," says Lee, who tried exactly one wonton noodle for taste. "I was so proud of myself for sticking to my plan."
The results were clear even before he hit the 4% body fat mark. He was leaner than he was portraying Bruce Lee, and, at 145 pounds, below his 150-pound high school body weight. It all worked toward Lee's big unveiling as shirtless Khan grimly prepares for battle in his yurt alongside Xian Lang. Even Lee was surprised when he took off his robe for the scene.
"You're just ripped, you look at yourself and it's like, 'Oh, my God, everything's there,' " Lee recalls feeling. "Niki came up to me afterwards and said, 'Thank you for your hard work, It's on film. It's forever.' "
Lee could focus on scenes of villainy, raiding, killing and a memorable scene where the riding Khan catches an arrow shot at him and shoots it back. While he often rode real "Mulan" steeds, that scene featured a prop horse in front of a wind machine. Lee amazed himself when he perfectly twirled the arrow in his hand to quickly fire back.
"The wind machine was blowing so strong that it blew the arrow backwards, so I was able to maintain control," says Lee. "I got so lucky. It looked so natural."
Following production, Lee says he contracted COVID-19 traveling to the London premiere of "Mulan" in March, which was ultimately canceled by the pandemic.
"My symptoms were very mild, three days of chills and body ache, then no sense of taste or smell, but a prolonged fatigue lasted a little over three weeks," he says. "Should've stayed home!"
The actor has experienced no residual effects ("Keeping vigilant and masked!") and says he's kept in shape during his COVID-19 quarantine at home in Hawaii.
But he's not Böri Khan-ripped. So he's thrilled to show his Hawaiian friends and former classmates how he rocks it in "Mulan."
"In Hawaii, everyone really cuts loose after age 35. My high school Class of 1984 classmates are going to be very shocked and jealous when they see me in this movie," he says.
This article originally appeared on USA TODAY: 'Mulan': Jason Scott Lee's epic journey to be ripped villain Böri Khan