"Batman: The Killing Joke" is one of the most definitive Joker stories out there and a big chunk of what makes it memorable are the events that occurred to Barbara Gordon. But while there appears to be an understanding that Barbara IS Batgirl, she never appeared in the story in costume. That's all going to change when "The Killing Joke" is adapted into an animated film.

In a leaked preview, director Sam Liu, producer Bruce Timm and DC Entertainment Creative Director of Entertainment Mike Carlin talk about the film, pointing out challenges went through in adapting the story.

For one, mimicking the art style of Brian Bolland was difficult. Liu and his team couldn't replicate it exactly so they took inspiration from art by Kevin Nowlan, going from there to a stripped-down version of Bolland's work for the animated film.

Another challenge for the team was how to handle Barbara's character. What happened to her has always been a sensitive topic so choosing to give the character her own story beyond that of a mere plot device is a good move. This also addressed the issue of turning The Killing Joke into a full-length feature without padding the story, according to Timm.

Carlin added that it was smart to go the direction of a prologue because it sets up Batgirl in action, helping make sense of who she is in the story.

"She wasn't just somebody's daughter, she was somebody who mattered to Gotham City, and Batman in particular," he said.

Given all that will happen in The Killing Joke, will it be getting an R-rating?

A high level of shock value typically warrants the rating but Timm is actually not sure what The Killing Joke will get. Considering what audiences are currently getting, he said it's possible for the animated film to get a PG-13.

Earlier in March, Kevin Conroy and Mark Hamill were confirmed to reprise their roles as Batman and Joker, respectively. They will be joined by Tara Strong as Barbara Gordon/Batgirl and Ray Wise as Commissioner Jim Gordon.

No release date has been provided for The Killing Joke but it is set to have a world premiere at the San Diego Comic-Con in July.

Watch the preview below!

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