Margot Robbie reveals Penguin was initially meant to be the villain in Birds of Prey.

Margot Robbie and Colin Farrell might have spent months side by side shooting their new fantasy romance A Big Bold Beautiful Journey (out September 19), but there’s one thing they never talked about on set: their secret shared past as Gotham’s most notorious troublemakers.

That funny realization came to them only during a recent Entertainment Weekly chat. Robbie—who’s forever etched in fans’ minds as Harley Quinn—suddenly turned to Farrell, who’s donned the prosthetics as the Penguin, and asked: “Did we ever talk about Harley and the Penguin?”

Farrell shook his head. “I don’t believe so.”

Both burst into laughter, marveling at how the topic somehow never came up. “We’ve talked about everything else, but not that? That’s so weird,” Robbie said.

Then Robbie dropped a surprising little Hollywood secret: in the very first draft of Birds of Prey, the Penguin was written as the film’s big bad. But that plan was scrapped when director Matt Reeves asked to reserve the villain for The Batman. Instead, the script pivoted to Black Mask, a role that eventually went to Ewan McGregor.

Farrell’s jaw nearly hit the floor. “No way!” he exclaimed. Robbie grinned and admitted the script is probably still sitting on her computer. “You can read it,” she teased. Without missing a beat, Farrell leaned in: “Send it to me, I’d love that.”

The exchange was just another reminder of the pair’s easy chemistry. Robbie has played Harley Quinn across three films—Suicide Squad (2016), Birds of Prey (2020), and The Suicide Squad (2021)—while Farrell transformed into Oswald “Oz” Cobblepot for 2022’s The Batman and spun the role into his own HBO series, The Penguin. He’ll also reprise the part in The Batman Part II.

As for Robbie’s Harley? DC Studios co-head James Gunn has hinted her future in the rebooted universe is still under wraps—but fans will “find out down the line.”

For now, audiences can enjoy seeing Robbie and Farrell step out of Gotham’s shadows and into something entirely different: a sweeping, romantic adventure that’s already bringing plenty of laughs behind the scenes.