When your friends tell you not to do something because you'll probably embarrass yourself, most people listen. Kevin O'Leary is not most people.

The Role Everyone Said He Should Skip

The Shark Tank star has officially crossed over into Hollywood with his debut in Marty Supreme, an upcoming sports comedy-drama set in 1952. O'Leary plays Milton Rockwell, a wealthy businessman with an edge—which, let's be honest, isn't exactly a stretch for him.

But when he first got the offer, the people in his orbit weren't exactly cheering him on. "So when I got offered this part, a lot of people that are around my sphere—advisors, agents, whatever—said, 'Don't do this…You don't know how to act,'" O'Leary told CNBC this week.

Fair point. Acting and negotiating equity stakes are different skill sets. But O'Leary saw something in the character that felt right. Director Josh Safdie called him up and explained they were writing Marty Supreme with a role specifically for him: Milton Rockwell, the richest man in America in 1952, and "a total A-hole." O'Leary's response? "Perfect."

Finding His Footing on a 1950s Set

Despite having zero acting experience, O'Leary jumped in headfirst. His first day on set involved shooting seven pages of dialogue with Timothée Chalamet and Gwyneth Paltrow—not exactly a low-pressure introduction to the craft.

What helped? The film's obsessive attention to period detail. The watches, the clothes, the entire environment screamed 1952, O'Leary said. After a few takes, "the cadence of the scene" took over and he found himself improvising naturally.

Working with Chalamet, who plays Marty Mauser, an aspiring ping pong champion, turned out to be a revelation. "There's sparks flying off that guy. He's amazing and all of a sudden you're in it and you don't even know your reading lines anymore, and that's the magic," O'Leary said.

What the Movie Is Actually About

Directed and co-written by Safdie, with a script by Ronald Bronstein, Marty Supreme is loosely based on the life of American table tennis player Marty Reisman. Paltrow plays Kay Stone, a wealthy socialite who forms a bond with Marty, and the cast also includes Odessa A'zion, Tyler Okonma, Abel Ferrara and Fran Drescher in supporting roles.

The film premiered at the New York Film Festival on October 6 and is set for a nationwide release by A24 on December 25, 2025. So if you're looking for something to do on Christmas Day besides arguing with your family, you can watch Kevin O'Leary prove his doubters wrong on the big screen.