Kevin O’Leary and Timothée Chalamet’s intense bare-butt paddle scene in Marty Supreme was just as crazy to film as it appeared on screen.

“We had a fake paddle that had a hinge thing and a foam thing. It was supposed to not hurt. Didn’t work. It broke immediately,” O’Leary, 71, exclusively told Us Weekly ahead of Marty Supreme’s Thursday, December 25, release. “So we got to a real paddle, wood, like, a real paddle, with grooves on the surface of it.”

O’Leary, who plays businessman Milton Rockwell in the biopic, explained that while there was an “ass double” for Chalamet, the actor ultimately wanted to be the one to perform the scene, which sees titular character Marty (Chalamet) asking Milton for forgiveness after passing on some exhibition ping pong matches. After Marty’s begging, Milton has the young athlete drop his pants and bend over for a spanking.

“Timmy walked in [and] said, ‘No, it’s got to be my ass. I’m going to immortalize my ass on film in perpetuity,’” O’Leary recalled, adding he tried to talk Chalamet out of it once he realized he was going to “hit” him with the nonprop paddle. “And he said, ‘I’m doing it.’ So we started whacking cheeks left and right and left and right to try and keep the red the same intensity.”

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While O’Leary “could feel the heat off” of Chalamet’s buttocks after about “20 takes,” director Josh Safdie told the Shark Tank star he was “not hitting him hard enough” and the scene didn’t “look real.” (“Now I know you’re a sick puppy,” O’Leary jokingly remembered thinking.)

“I wound up like a baseball bat, and I nailed his right cheek, and I think his eyeballs exploded out of his head, and that’s what you see,” O’Leary said of the take used in the final edit. “His reaction to that was still just great.”

O’Leary confessed he was impressed with what a “crazy trooper” Chalamet was on set.

“I have a new respect for that kid,” he said. “There’s no question about it. And he deserves an Academy Award.”

In recent weeks, Chalamet has echoed similar sentiments about his performance, which he has deemed award-worthy. The Dune star ultimately received backlash for his confident stance, but from O’Leary’s perspective, Marty Supreme is unlike Chalamet’s previous roles.

“I went out of my way knowing I was going to be across from him to watch all his stuff, the Dune stuff, everything [is] so good. And I can tell you with certainty, and I’m right about this, this is his best performance by a factor of 100 percent,” O’Leary told Us. “It’s beyond anything he’s ever done. And he went to a new place. He just did. And I was there. I watched it happen. I was in the room, saying, ‘Wow, this guy is f***ing crazy.’”

Coming from the world of reality TV, seeing Chalamet’s process for getting into character as Marty was a whirlwind experience for O’Leary due to his ability to “riff” and “improv.”

“When I saw the final cut, they took scripted lines and merged them in with riffs that were improv, And that’s why the kinetic energy is there, the best of the best of every scene. Even though it was a mistake,” he said. “Chalamet kind of works in every scene where he gets up, comes back, sits down, and he’s in Marty, like, he’s not Chalamet anymore. He’s Marty. And the sparks are flying off him, and if you’re crossing him, you’re just going at him.”

Marty Supreme follows up-and-coming table tennis star Marty Mauser’s journey to become a professional champion, following him on his journey from the Lower East Side to international tournaments. . The sports comedy is loosely based on the career of real table tennis pro Marty Reisman.

O’Leary made his acting debut in Marty Supreme after being one of the iconic moguls on Shark Tank for nearly two decades. The business mogul explained that while he was excited to give acting a try, some of his team members weren’t sure if he could make the transition.

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“‘Look, Kevin, this is acting. This is a script. This is scripted. You are not a scripted guy. You’re a reality guy. We have built a big franchise with you,’” O’Leary recalled someone from his team saying. “He said, ‘I have to be transparent with you … as your representatives some of us don’t like it. We think you’re going to s*** the bed.’ Those are the words he used.”

Despite the naysayers, O’Leary was adamant he was going to try something new.

“And I said, Well how do you know I’m going to s*** the bed? How does anybody know anything until I try it?’ Because I think you want to keep your life interesting, you got to go out of your comfort zone,” he reflected, “And so they sent the script over.”

After printing out the script, one of O’Leary’s friends saw paper on the businessman’s deck and decided to read it while watching the sunrise. The pal, who was unfamiliar with Safdie’s work, was captivated by the story.

“He says, Kevin, who wrote this? What sick puppy, screwed up, crazy person wrote this?’ I said, ‘Why are you asking?’ He said, ‘This is sick. It’s sick, but I can’t stop reading it, and I can’t stop and you have to be this guy, Milton Rockwell,’” he explained. “It’s crazy … that got me because here’s some random guy, he [didn’t] know anything about the story, and he was hooked, like, just riveted. And I thought, ‘S***, this is going to be a good movie.’”

Still, O’Leary didn’t make it easy for Safdie. When asked if he could meet them in New York to discuss the project, O’Leary countered with an offer to fly to him in for a meeting at his lake house near Toronto.

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“I said, ‘How about [a] new idea I’ll send a plane. You get on it, you fly up here, and we read this together on my dock with the ducks going by and the sun setting and rising, peaceful environment,” he recalled. “And I thought it was also a bit of a test to see how serious they were, because if they’re going to do that, then they must be serious. So they did it, and they came up.”

Despite being excited to take on the challenge of Rockwell, O’Leary admitted he was initially “dissatisfied” with his character’s ending — but worked with Safdie to deliver something he felt was justifying for Milton’s journey.

“If I’m really Milton Rockwell, I would never let this little fer do this to me, and I would rip his fing heart out,” he quipped adding that he ended up collaborating with the writing team for a different ending. “That changed my whole view about things, because the ending we came up with on a collaborative basis. I’m not going to say I wrote it, but I told them that I was unhappy, and they gave me a path to where I was happy. And I’m very happy with the way it ends.”

Marty Supreme hits theaters on Thursday, December 25.