Just a few days after word began circulating that Jared Leto is being eyed for the role of the Joker in "Suicide Squad," Collider has heard from an unnamed source that actress Margot Robbie has signed on to play the Bat-villain's main squeeze -- Harley Quinn. Robbie is best known for her role in Martin Scorsese's "The Wolf of Wall Street" and has been on a shortlist of celebrities rumored for roles in the supervillain team-up movie. Director David Ayer has reportedly been courting Will Smith and Tom Hardy in addition to Leto and Robbie. With Robbie possibly signed on already, the other rumored actors may not be far behind. The Wrap reported on Friday that Smith, Hardy and Leto were all in various stages of discussion regarding starring in the film, and that Jesse Eisenberg's Lex Luthor is scheduled to make an appearance. Casting on the film will have to commence soon as "Suicide Squad's" release date is fast-approaching. The movie will be the first of Warner Bros. massive film slate to hit theaters after 2016's "Batman V Superman: Dawn of Justice." Unlike the Joker and Lex Luthor, two characters with tangential ties to the Squad at best, Harley Quinn has been a major part of the unit's ongoing series since the launch of the New 52 in 2011. Quinn has also emerged as one of the biggest breakout stars in the publisher's new era; her ongoing solo series is a massive hit, with "Harley Quinn Annual" #1 outselling every other DC Comic other than "Batman" #35 last month.