‘The Penguin’s’ Colin Farrell and Cristin Milioti reveal the secrets behind their transformative performances (being huge Bat-fans helped)

Colin Farrell found a novel way to test-drive the makeup devised for his portrayal of the sociopathic mobster Oz Cobb: He went to Starbucks in the elaborate regalia he’d ultimately disappear into to play The Penguin’s fowl felon.

"We went to a Starbucks when we did the first makeup test," Farrell revealed during an FYC panel for the HBO series, which spun off from the film The Batman, in which he initially played the role, clocking the coffee shop to gauge the reactions of his fellow customers to his foreboding, scar-pocked façade. "But nothing happened!" the actor confessed, adding that he also used the character's distinctive voice and shambling limp on the foray. "We're a bunch of starers — human beings stare if they see something different. But they just stared at their phones."

Still, moving about unnoticed in public was a victory in and of itself given the extreme nature of Farrell’s transformation — so metamorphic that it boggled even the actor’s own mind. "It was just weird," he said. "Talk about a personalized uncanny valley... And it never fully lost that either. I never fully got used to looking in the mirror and seeing that image look back at me. It was a very powerful thing."

What didn’t work, though, was Farrell’s attempt to stay method by employing that signature waddling gait at all times. "I made the decision: 'I'm just going to walk-waddle like this the whole time,'" he explained. "And on Day 2, in between takes, it's like, 'F--k that!' Yeah, no, my hips couldn't take it, and I was a bit banjoed for a couple of months afterwards. Just was a bit."

Getting to disappear underneath Oz’s craggy, bulky exterior was a long-awaited dream for the actor. "I was so overwhelmed by the beauty of the makeup, I really was," he said. "I was so overwhelmed by it. I grew up watching John Landis' 'Thriller' video, and I grew up on Planet of the Apes and Dick Smith's extraordinary job. The Thing by John Carpenter is one of my favorite films, and Rob Bottin's work on that. So the idea of practical makeup, tangible things that become so real to the viewer as they did for me, I was just so giddy by it, and I knew that we could go other places with it."

Farrell said the minute detailing in Oz’s face offered him a roadmap to build the character out from. "I learned as much from looking at what Mike [Marino] designed as I did from what we usually learn our tricks from, which is the written word of the writer," he explained. "There was such a sense of history to Oz: a lonely, broken character, and obviously not to be trusted. It felt very human to me, and he does definitely have a heart, but just as dark a character as I'd ever like to explore, to be honest with you."

He also conceded that his own efforts to etch out the Penguin’s prior history ultimately ran afoul of what showrunner and executive producer Lauren LeFranc was concocting for the series.

“It's just fun… Write a little prose and just give your imagination license — and then I found out the backstory when Lauren pitches the show, and it didn't match at all," he laughed. "But I could hold on to a couple of little events that took place when Oz was 16 and 24 and some bare-knuckle fights and being in a lane way one day and getting opened by a bottle and stuff. It's a lot of trauma on his face, a lot of trauma in his physicality as well as a child, to have such blatantly obvious physical impedance in your life as we know what kids are like. [Oz] would've grown up around a lot more cruelty than we had the time or the inclination to get into in the show. But that was all there: a very damaged character."

Farrell considers finding the sweet spot where the writing, his performance, and the makeup artistry merged as one of the most significant moments of his long career. “I've had extraordinary days over 25 years of being an actor, but it was one of the most extraordinarily exciting days, the idea of entering Gotham," he said. "I grew up watching Burgess Meredith. I grew up watching Danny DeVito, and the idea that I was going to get to play the Penguin!"

Farrell’s fandom for the Dark Knight’s extensive filmography was matched by that of co-star Cristin Milioti, who played the tormented Sofia Gigante, the sheltered then abandoned scion of the mob family who craves vengeance. Joining Farrell, fellow cast members Rhenzy Feliz and Deirdre O'Connell and LeFranc and executive producer Dylan Clark for the panel at the Paramount Theatre on the fabled Paramount Pictures Studios lot, Milioti revealed her Bat-fangirl bona fides.

"I've been such a huge fan of this universe forever," the actress enthused. "Every iteration of Batman — even Batman Forever. I mean, Batman Returns was the first one I saw, and then I made my dad take me to see Batman Forever — five times... I love this universe. I think you're able to do these grounded things. Obviously some of the versions go to very heightened, campy places, but still, even those versions I would find devastating because they're all about loneliness and hurt. All of them. Even when you're even Batman, all of them."

Milioti was eager to throw herself into the role. "Before we started shooting, I had hours of conversations that Lauren was very sweet to entertain and take my call each time, and then I got to read the first four [episodes]," she said, indicating the big reveal behind Sofia’s history. "So I knew about [the fourth episode] when we were going in, and that was my bible for everything."

That time-spanning fourth episode also had a truncated production timeline, requiring Milioti to play Sofia in different eras of her life in a single day. "I would be her 10 years apart," she noted, "but also the sort of chaos of it can sort of sweep you along. Some days it's frustrating, but for the most part you just feel like you're on this roller coaster and I really deeply, deeply loved it."

And like Farrell, she found herself adopting a signature style of walking when costumed in Sofia’s final look, with wild hair, warpaint makeup, vampish red-draped gown and stiletto heels. "If you wear that, there's a certain way you've got to walk," she laughed. "Put that on and light three cigarettes, I dare you, and try not to feel great."