Without knowledge of the casting list, it would be virtually impossible to name Colin Farrell as the actor playing Oz Cobb in The Penguin. That’s a credit to the incredible prosthetics and makeup applied to Farrell to complete the unrecognizable transformation.

When crafting the character for The Batman, director Matt Reeves focused on Oz’s motivations over physical features. Reeves sought inspiration from a specific character in The Godfather.

“We talked a lot about Fredo,” Reeves told Deadline. “We talked about John Cazale in The Godfather and the idea of maybe trying to give him a penguin nose or doing something to kind of mess up Colin’s face to get the sense of somebody who’d been overlooked, somebody who had this ambition inside of him, but who was mocked and who had been looked down upon.”

With the spirit of the character finalized, Reeves’ attention turned to Oz’s appearance. Enter prosthetics designer Mike Marino, whose pitch for Oz changed everything.

“All of a sudden one day, Mike Marino said, ‘Let me show you what I’ve been working on,'” Reeves explained. “Mike is an incredible artist, and he did this sculpture. I’m telling you, the sculpture was exactly the way that Oz looks right now. It’s incredible. And I was like, ‘Wait, what?’ We had never said, ‘Let’s just take Colin and turn him into something that we’ve never seen before.’ I said, ‘this is Colin Farrell. I got to now tell the studio he’s not going to look like Colin Farrell.’”

Luckily for Reeves, HBO believed in the vision and supported Farrell’s transformation from the get-go.

“I was never nervous,” said Sarah Aubrey, HBO Max’s Head of Originals. “We got an early glimpse of Colin’s work as Oz in The Batman and knew that this was a powerhouse performance … ferocious, witty, vulnerable, diabolical. And all of that could be the jet fuel for an epic series.”

Applying a mountain of prosthetics and makeup takes time. Farrell told Jimmy Fallon that he spent three hours in the makeup chair every morning to play Oz. The arduous process ended up aiding Farrell’s performance, allowing him to slip more easily into character.

“When I looked into the mirror for the first time and I saw Oz looking back, it was really powerful,” Farrell said in the same Deadline interview. “There’s a kind of essence of possession. If you give yourself over to it, it tells you so much. You start to move a different way. You start to look a different way. You start to feel powerful.”

The Penguin premieres on HBO and Max on September 19.