Margot Robbie has spent the last few years establishing herself as quite the power player. The actress broke out in Martin Scorsese‘s The Wolf of Wall Street and has steadily climbed her way to the top ever since, but she’s not just an Oscar-nominated actress — Robbie wasted no time setting herself up behind the scenes as a producer with her banner Lucky Chap. And it was her dang idea that got Warner Bros. upcoming Birds of Prey and the Fantabulous Emancipation of One Harley Quinn started in the first place.

Earlier this year, I visited the set of Birds of Prey in Burbank, California, where I joined a small group of journalists to tour the stages and chat with the filmmakers. During a break in the shooting schedule, Robbie sat down in full Harley Quinn costume for an interview and discussed how the film went from an idea on the set of Suicide Squad to a full-blown superhero blockbuster — and it turns out, it all started with the character of Huntress (played by Mary Elizabeth Winstead in the film).

“Well, I first actually pitched the notion when we were actually still shooting Suicide Squad, cause I kept saying like, ‘Oh, Harley does so much better when she has people to play with.’ I kept thinking that in real life I had such a girl gang, like my group of girlfriends, and I just want Harley to have a girl gang,” Robbie explained. “I just want it to be like a girl gang for Harley to be a part of. And then obviously I’d been reading a ton of the comics, anything involving Harley, and one of the separate line of comics is the Birds of Prey, which I started reading. And Harley’s not a traditional member of the Birds of Prey, but it was a fun kind of girl gang to kind of dip in and out of, I suppose.”

“It really started with Huntress,” Robbie continued. “I just loved Huntress, and with my initial pitch on the story, I said I wanted to keep it quite contained, get no bigger, and no world-ending stakes. Like the stakes were as big as perhaps mafia level or gang level. That’s when I started reading a lot of Huntress comics, obviously coming from a mafia family, and found her story. Plus, I always gravitate… well, not always, but I do often gravitate towards a revenge story because it is so straight forward, but you are so clearly motivated.”

Once she landed on the Huntress idea, it was all about filling out the ensemble with exciting characters that worked with Harley (and that were available on the studio level, unlike Batgirl, who is traditionally a founding member of the Birds of Prey.)

“After Huntress, it kind of fleshed out from there. Which other members kind of counterbalance her revenge story, and Harley’s version of what’s right and wrong? You kinda needed a more moral character like Renee Montoya. We needed a cop in there. Canary obviously is so crucial to the Birds of Prey, we really wanted to introduce her as well. And then Cas — Christina [Hodson], the writer, and I actually spoke about a lot of our favorite films, and wanted to pay homage to a few things, but, Leon The Professional was one of them, and we just loved that relationship – the, mentor and mentee, a very unexpected friendship there. We kind of found ourselves gravitating towards that as well.”

Ultimately, that led Harley’s girl gang that’s headed to theaters next year — Robbie as Harley, Winstead as Huntress, Rosie Perez as Renee Montoya, Jurnee Smollett-Bell as Black Canary, and Ella Jay Basco as Cassandra Cain.

We’ll see how the gang of heroes, anti-heroes and everything in between comes together when Birds of Prey arrives in theaters on Feburary 6, 2020.