Margot Robbie's Harley Quinn became so popular after her role in "Suicide Squad." The Australian actress portrayed the villainess so well that she was chosen to star in yet another DC blockbuster, "Gotham City Sirens."

Robbie was recently spotted at the LAX with a certain "Harley Quinn" comic book in her hand. The photo of her, which was posted on social media, sparked reports that she was doing research for "Gotham City Sirens." Shortly after the photo became viral, an astute fan found out exactly what comic book issue she was reading.

In this issue, which is the "Harley Quinn Valentine's Day Special" in "Harley Quinn Vol. 3 Kiss Kiss Bang Stab," Harley gets a chance to go out on a date with Bruce Wayne because of a charity auction. The villainess eventually decides to kidnap the Caped Crusader instead.

Screen Rant has pointed out that this story arc does not seem to be part of the plot for "Gotham City Sirens." However, the actress could merely be looking to draw inspiration for her character.

Furthermore, Ben Affleck is also expected to at least make a cameo in the film. He already appeared in two DC movies and is reportedly slated to show up in "Justice League" and "Wonder Woman." Batman's appearance in "Gotham City Sirens" will make sense primarily because he has history with all three women - Harley, Catwoman, and Poison Ivy.

Since it was confirmed that the project got a green light for pre-production, DC fans have been at a frenzy trying to guess what the film is going to be about. The only detail that is known about it is that Harley will be joined by two other female villains to Gotham City, namely, Poison Ivy and Catwoman.

To date, it remains unconfirmed if "Gotham City Sirens" will be inspired by the comic book that Robbie was spotted reading. It is either part of the upcoming film's narrative, or the "Suicide Squad" star was merely teasing DC fans.