Efron spoke with ET alongside co-stars Jeremy Allen White, Stanley Simons and Harris Dickinson.
The stars of The Iron Claw are getting into the nitty-gritty of how they bonded on set.
On Monday, ET's Cassie DiLaura spoke with Zac Efron, Jeremy Allen White, Harris Dickinson and Stanley Simons about how they transformed into the famed Von Erich wrestling brothers for their new film and why that included shaving their chests as one of the first things they did all together.
"I don’t know if that was the very first," said Simons, who portrays Mike Von Erich -- the fourth brother.
Efron plays Kevin Von Erich, White plays Kerry Von Erich and Dickinson plays David Von Erich. The Von Erich brothers spent the majority of their careers in World Class Championship Wrestling (WCCW), where they won multiple individual and tag team titles.
"But it was close to it," Efron, 36, joked.
"We might have had a couple of, like, training sessions or something, but it was early," White, 32, added.
"We had practices -- something in the ring, we were working with Chavo on wrestling moves -- and then I think, yeah, very quickly after that we were all lined up in a row getting our bodies shaved and wigs applied," Efron responded. "And like glitter and tan and stuff like that."
"Yeah, greased up," Simons said.
Luckily for the on-screen brothers, being thrown into the deep end when it came to preparing for the film helped them become comfortable with each other rather quickly. After getting "greased up" together, their egos and fears took a backseat role.
"From that point forward, it was all easy because we really had nothing to hide from each other," Efron said.
One thing that impressed the bunch while filming? Efron's impressive lack of training needed for a dance scene.
The group told ET that while they all went through practices to get camera ready for a choreographed scene set at Kevin Von Erich's wedding, Efron -- a movie musical alum with roles in Hairspray, The Greatest Showman and High School Musical under his belt -- did not need to practice.
"We embarrassingly had, like, a full afternoon of [dance] training for the three of us," White said.
"Zac was busy shooting so he showed up [on the day of the dance scene] without any -- without any prior training and he crushed it," Simons added. "He was better than all of us."
While he may have made it look easy to the other three, the 17 Again alum said it required an entirely different set of muscles that he hadn't used in a while.
"Going from wrestling to dancing, it's kind of weird because we're doing such big moves and jumping off ropes. We're getting used to that kind of action. So when you -- it's shocking you can just do a little bit of, like, square dance and you're, like, about to pull a hammy," Efron joked.
Additionally, Simons said that he learned the song "Breaking Free" from High School Musical and sang it on set to try and impress his co-star, which Efron said "worked."
"He crushed it. Also worked really well for the characters because I think it just like, it made me embarrassed, like most definitely blushing," the Baywatch star said. "It was hilarious. I'm gonna get you back for that."
On Monday, as he was awarded a star on the Hollywood Walk of Fame, Efron admitted that while he may have left the role of Troy Bolton behind more than a decade ago, he still revisits the iconic songs every now and again.
"I'm eternally grateful," he said. "I still think about [High School Musical] every day. I sing the songs in the shower. Go Wildcats!"
You can watch the trailer for the film in the player below:
The Iron Claw releases in theaters on Dec. 22.
For more coverage of the film, check out the links below.
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