Finally, R-rated animated adaptation of the iconic graphic novel, scheduled to release in July of 2016, featuring the return of Kevin Conroy and Mark Hamill to their iconic voice roles as Batman and The Joker, respectively. To prep for the highly-anticipated animated film, here are 15 Things You Need To Know About Batman: The Killing Joke.

15. Concept & Background Info

Although Alan Moore wrote The Killing Joke and is typically recognized with ideating the concept, it's actually Brian Bolland who conceived the idea for the novel after watching the 1928 film The Man Who Laughs. The film's titular character, Gwynplaine, played by Conrad Veidt, specifically his perpetual grin.

Batman co-creator Bob Kane confirmed the notion in a 1994 interview with journalist Frank Lovece: “[The Joker] looks like Conrad Veidt — you know, the actor in The Man Who Laughs, by Victor Hugo. Finger had a book with a photograph of Conrad Veidt and showed it to me and said, ‘Here’s the Joker.’”

In 1984, then DC Comics editor Dick Giordano allowed Bolland to conceptualize any DC project he wanted, and his heart fell on giving The Joker and origin story. Following the release of Alan Moore's ground-breaking graphic novel, Watchmen, Bolland requested Moore pen The Killing Joke, and together they created the greatest Joker story ever told.

14. Alan Moore & Brian Bolland

Alan Moore is considered by many to be the greatest graphic novel writer in history, having penned genre-defining works such as Watchmen, V for Vendetta, From Hell, and, of course, Batman: The Killing Joke. He began his career writing comic strips in Britain before being picked up by DC Comics in the early '70s, thus paving the way for future British comic writers. His works are often interlaced with profound symbolism and adult themes, looking to challenge the foundation of the subject matter at hand, which is evident in The Killing Joke.

Brian Bolland, on the other hand, is a famed comic artist, though he has also written comics sparingly over the years. He is credited with driving the British Invasion into American comic books in the late '70s/early '80s, along with fellow comic writers/artists Alan Moore, Neil Gaiman, and Grant Morrison, consequently leading to DC Comics creating the more mature-oriented Vertigo imprint. Along with Moore, Bolland has won numerous Eisner Awards, including one for The Killing Joke in 1989.

13. Joker's origin story

One of the most perplexing and longest-running mysteries in comic book history is permanently altered his appearance, leaving him with green hair, ruby red lips, and stark white skin.

Alan Moore and Brian Bolland used the concept envisioned by Finger to create The Joker's origin story in The Killing Joke. the Red Hood in order to procure enough money to his pregnant wife. Unfortunately, leaping into a basin of chemicals left him disfigured, and coupled with the death of his wife, the comedian succumbed to darkness and became The Joker. Although many consider this to be The Joker's definitive origin story, Bolland has reiterated multiple times that it is just one of many possibilities. After all, even The Joker cannot recall his own origin, having said in The Killing Joke: “Sometimes I it one way, sometimes another. … If I’m going to have a past, I prefer it to be multiple choice! HA HA HA!”

12. Barbara Gordon aka Batgirl

While The Killing Joke is brimming with thematic changes to the Batman comics, what the novel is most well-known for is being Barbara Gordon's concluding chapter as Batgirl. Although DC Comics officially retired the character in the one-shot comic Batgirl Special #1, many people consider The Killing Joke to be the definitive conclusion of Barbara Gordon as Batgirl.

In the novel, The Joker shoots Barbara Gordon at an amusement park, thus rendering her paraplegic, and then, subsequently, takes several photographs of her. He later kidnaps her father, Commissioner Jim Gordon, strips him, cages him, and forces him to view the photos he took earlier of Barbara. Although Batgirl was only briefly featured in the novel, her presence is of utmost importance to Batman and Commissioner Gordon's story, and will be featured more prominently in the animated movie.

Of course, with a character like Batgirl, she couldn't stay dead, so to speak, for long. Eleven years after retiring the character, DC Comics introduced a new Batgirl in the story arc "No Man's Land," with former Huntress, Helena Bertinelli, donning the costume.

11. "One Bad Day"

At the height of the story, The Joker's henchmen strips and cages Commissioner Gordon, while the Clown Prince of Crime forces him to view photos of his wounded daughter, Barbara, all in an attempt to drive the Commissioner insane. When Batman chases after The Joker in the fun house, he reveals to The Dark Knight that even if he is caught, it wouldn't matter, for he has succeeded in driving Jim Gordon mad. "All it takes is one bad day to reduce the sanest man alive to lunacy. That's how far the world is from where I am. Just one bad day," Joker tells Batman.

The Joker's iconic quote has been an influence for comic book writers over the years, and can even be viewed as potentially inspiring quotes from other comic book characters. For instance, in the latest season of Marvel's You're just one bad day away from being me," an apparent reference to The Joker's "one bad day" line (although the reference has not been confirmed).

10. Impact on the Batman mythos

There isn't a more poignant and affecting Joker story in the DC Universe than Alan Moore and Brian Bolland's The Killing Joke. Although the duo initially conceived the story as being a standalone one-shot comic (in the comic book industry, a one-shot is a self-contained story, usually having no last effect on general continuity), the story ended up being partially canonized in the official DC Universe.

As previously mentioned, while Barbara Gordon officially retired the Batgirl superheroine in July 1988, The Killing Joke is widely regarded as being the character's final chapter, having been ruthlessly paralyzed by The Joker. While the Clown Prince of Crime has toyed with the Batman over the decades, The Killing Joke marked the first time the Killer Clown profoundly impacted a member of the Bat-family, which paved the way for Jim Starlin's Batman: A Death in the Family later that year.

After spending the entirety of the Silver Age of Comics painting The Joker as a wacky lunatic, The Killing Joke followed Frank Miller's The Dark Knight Returns and restored the Clown Prince of Crime back to his darker, grittier roots, thus allowing him to become Batman's arch-nemesis once again.

9. Critical & fan reception

Batman: The Killing Joke was not only a commercial success but a critical one as well, having won an Eisner Award (the comic book industry's equivalent to Hollywood's Watchmen a year earlier.

Although the graphic novel is widely acclaimed -- by both critics and fans -- its themes and brutality have prompted controversy in the industry as well as widespread feminist backlash. In fact, the extent to which The Joker mutilated Barbara Gordon became an inspiration for the Women in Refrigerators movement in the late '90s, which sought to bring light to the common comic book trope of female characters being either injured, killed, or depowered as a plot device.

8. "No Joke"

Along with other acclaimed story arcs in the '80s, Booster Gold, a time-traveling superhero from the future, to create a companion story for The Killing Joke.

In Booster Gold #5, "No Joke," the eponymous superhero is tasked by his father and Time Master Rip Hunter to travel back in time and prevent The Joker from shooting and paralyzing Barbara Gordon at the run-down amusement park. In the companion story, Booster Gold arrives at the climax of The Killing Joke, just prior to The Joker taking photos of a wounded Barbara Gordon. Unfortunately, after fending off The Joker's henchmen, Booster Gold is too late to save Barbara. He is instead caught by the Clown Prince of Crime and beaten to a pulp.

Rip Hunter rescues Booster Gold just mere moments before The Joker kills him, and pulls him back to their time. Booster Gold attempted several times to save Barbara, but Rip Hunter later reveals that Barbara's paralysis is inevitable, for she is destined to one day become Oracle. However, despite failing to save Barbara, Batman thanked and befriended Booster Gold for at least trying.

7. "Ladies' Night"

Shortly after taking over the ongoing anthology series The Brave and the Bold, writer J. Michael Straczynski and artist Cliff Chiang wrote a one-shot prequel comic to Moore and Bolland's The Killing Joke, The Brave and the Bold #33, "Ladies' Night," which partly takes place simultaneously to The Killing Joke.

In the story, Wonder Woman were incapable of preventing the incident from transpiring. So, Zatanna planned a very special girls' night out with Batgirl and Wonder Woman, which included dancing -- lots of dancing.

Interestingly, the comic reveals the inspiration for the code-name Oracle, which Barbara later assumes. The name comes from the Oracles at Delphi, who could predict the future but if they tried to change it, the consequences could be "a thousand times worse." However, they were also known for providing key information and being the oracles of prophecy.

6. The New 52

In 2011, Geoff Johns and artist Andy Kubert created the massive DC Comics crossover event alternate, apocalyptic future. Once he realized his mistake, Flash traveled back once again and stopped his earlier self from changing the past, which in turn created the relaunched New 52 universe.