Alan Moore and Brian Bolland's graphic novel, Batman: The Killing Joke, is almost universally considered to be the greatest Joker story ever told. The one-shot comic -- loosely based on previous comics -- simultaneously tells one of many possible origin stories for Batman's arch-nemesis, The Joker, in addition to showing the Clown Prince of Crime attempt to break Gotham City's Police Commissioner and Batman ally, Jim Gordon. No story has been more influential for the killer clown, and perhaps no story before or since has been more fundamental to the Batman mythology.

Finally, after years and years of waiting, DC Entertainment announced last year that they will be making an 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

Conrad Veidt in The Man Who Laughs and The Joker 1941

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, is credited with inspiring the look of The Joker, 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

Comic book writer Alan Moore

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

The Joker's Origin Story in The Killing Joke

One of the most perplexing and longest-running mysteries in comic book history is the origin of Batman's perennial enemy, The Joker. Early in the Silver Age of Comics, Batman co-creator Bill Finger was inspired to give The Joker an origin story in Detective Comics #168, "The Man Behind the Red Hood." As the story goes, The Joker was once a lab scientist who attempted to steal from the Monarch Playing Card Company when he was caught by the Batman. In order to escape, he leaped into a chemical vat which, then, 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. In the novel, The Joker was once a failed comedian who turned to a life of crime as the Red Hood in order to procure enough money to support 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 remember 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

Batgirl in The Killing Joke

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 upcoming 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"

The Killing Joke "One Bad Day" quote

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 Daredevil TV series, The Punisher tells the Devil of Hell's Kitchen, "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

The-Killing-Joke

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 sets release date

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 Academy Awards; established in 1988) for Best Graphic Album in 1989. At the same awards ceremony, Alan Moore won Best Writer for The Killing Joke. He nabbed two consecutive wins that year, having won Best Graphic Album and Best Writer for 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"

Booster Gold in "No Joke"

Along with other acclaimed story arcs in the '80s, such as Crisis on Infinite Earths, The Killing Joke received a follow-up story in the mid-2000s. In 2007, writers Geoff Johns (now head of DC Films) and Jeff Kurtz used 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"

Batgirl and Wonder Woman in The Brave and the Bold "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, Zatanna, one of the most powerful sorceresses in the DC Universe, had a precognitive dream showing The Joker shooting and paralyzing Barbara Gordon. Unfortunately, similar to the circumstances seen in Johns' "No Joke," Zatanna and 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

The New 52 Batgirl leaps into battle in DC Comics.

In 2011, Geoff Johns and artist Andy Kubert created the massive DC Comics crossover event Flashpoint, in which Barry Allen aka The Flash traveled back in time and prevented his mother's murder, thus leading to an 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.

When DC Comics launched their 52 new titles, many characters, origins, and stories were altered. For instance, Wally West aka Kid Flash, who everyone grew up loving, was recreated and given a vastly different origin story. While many things changed, some elements -- more specifically, stories -- remained intact, and one of those stories was The Killing Joke. In the new universe, however, Barbara Gordon recovered from her paralysis and resumed fighting injustice as Batgirl, although it is revealed that she suffers from post-traumatic stress as a result of being shot by The Joker.

5. Animated Movie

Batman: The Killing Joke - Mark Hamill as The Joker

In 2011, legendary voice actor Mark Hamill revealed an interest in voicing The Joker in a potential animated adaptation, though the idea for the movie didn't come to fruition until four years later. Bruce Timm announced the Batman: The Killing Joke animated movie during the Justice League: Gods and Monsters panel at San Diego Comic-Con 2015, stating that he would executive produce with Sam Liu directing.

Although it was heavily rumored, Kevin Conroy and Mark Hamill weren't officially revealed to be voicing the titular characters -- Batman and Joker -- until March 2016, along with Tara Strong and Ray Wise voicing Batgirl and Commissioner Gordon, respectively. Even though the movie is considered to be one of the most anticipated DC animated movies ever, Hamill further hyped the release by reading a line from the movie, as The Joker, during a panel at Star Wars Celebration 2016.

In addition to premiering at San Diego Comic-Con 2016, Batman: The Killing Joke will screen in over 1,000 theaters -- one-night-only -- on July 25th, at 7:30 pm and 10:30 pm, accompanied with a special introduction by Hamill. The film releases on Digital HD on July 26th, followed by a Blu-ray & DVD release on August 2nd.

4. Mark Hamill & Kevin Conroy

The Killing Joke - Batman threatens the Joker

To common moviegoers, Mark Hamill is known for playing Luke Skywalker in the Star Wars saga; however, he has an extensive resume filled with notable voice acting gigs. In fact, to geeks and many DC Comics fans, he's considered to be the definitive Joker. Hamill voiced the iconic supervillain in both the acclaimed Batman: The Animated Series and Superman: The Animated Series (along with several other animated shows), Batman: Mask of the Phantasm, and Batman Beyond: Return of the Joker, as well as Rocksteady's Arkham video game series. Thankfully, he hasn't shown any sign of stopping soon, despite previously held beliefs that he had retired from the role.

Along with Hamill, Kevin Conroy is considered by many to be the definitive Batman, having voiced the character throughout Batman: The Animated Series and in the fan-proclaimed DC Animated Universe, also referred to as the Timmverse (named after producer Bruce Timm). Conroy has voiced Batman in virtually all of the aforementioned adaptations featuring Hamill as The Joker. He reprised his role as the Caped Crusader in the series' final installment, Batman: Arkham Knight. Above all, Conroy and Hamill are considered to be the exemplification of what Batman and Joker should be like.

3. Influence on Batman movies

Heath Ledger's Joker From The Dark Knight

While Moore and Bolland's The Killing Joke has never been given a direct adaptation (until now), that's not to say elements of the iconic novel haven't been appropriated before. In the acclaimed animated movie Batman: Under the Red Hood, based on the comic book story arc of the same name by writer Judd Winick and artist Doug Mahnke, the Red Hood lures Batman to the Ace Chemical plant, where Joker jumped into a chemical vat, permanently disfiguring himself and, thus, becoming The Joker.

In addition to being recounted in Batman: Under the Red Hood, The Killing Joke has influenced both Tim Burton and Christoper Nolan's live-action Batman movies. In a 2006 interview, Heath Ledger revealed that while he hadn't read any Batman comics prior to being cast as The Joker in Nolan's The Dark Knight, shortly after accepting the role, he was given a copy of The Killing Joke to study. However, unlike the novel's direct influence on Nolan's Joker, Burton's now-iconic 1989 Batman film wasn't directly inspired by The Killing Joke; rather, the graphic novel inspired Burton to create an ominous Batman movie featuring the Caped Crusader's perennial enemy at the helm.

Additionally, judging by first-look photos and everything else we've seen thus far from David Ayer's Suicide Squad, Jared Leto's Joker appears to have been -- at least partially -0 inspired by The Killing Joke.

2. Other Borrowed Adaptations

Mark Hamill's Joker in Arkham City

As previously mentioned, Liu and Timm's Batman: The Killing Joke animated movie is the first true adaptation of Moore and Bolland's graphic novel, although there have been several television shows and video games -- in addition to the aforementioned movies, of course -- that have borrowed elements from The Killing Joke. For example, in the prologue for the TV series Birds of Prey, Barbara Gordon is shot by The Joker as she opens the door and is subsequently paralyzed. Also, in The Batman animated series (not to be confused with Batman: The Animated Series, a far superior effort), Joker tortures and breaks Detective Ethan Bennett, thus turning him into Clayface, similarly to how Joker tortured Gordon in The Killing Joke.

While the above two TV series have adapted elements from the novel, Rocksteady's Arkham video game series is a direct continuation of the events from The Killing Joke. Not only does Barbara Gordon feed information to Batman as Oracle, but The Joker's origin is recounted in Batman: Arkham City. Later, in Batman: Arkham Knight, Batman hallucinates several of his most haunting moments, including when Joker shot Barbara. Additionally, Joker's Hawaiian attire is available to wear in multiple video games, including Injustice: Gods Among Us.

1. Legacy

Batgirl Movie Barbara Gordon

By now, it is painfully obvious that Alan Moore and Brian Bolland's 1988 graphic novel, Batman: The Killing Joke, is not only the greatest Joker story ever told, but also one of the darkest stories in comic book history. The novel has inspired countless Joker stories since its release, and will continue to do so for years to come, especially since Sam Liu and Bruce Timm's animated movie is expected to be a hit. But that's not to say people haven't looked back on the novel with a level of discontent.

Despite being an overwhelming success, Moore and Bolland have both been open about their apprehension towards Batman: The Killing Joke. Moore has reiterated multiple times that they went too far having The Joker torture Barbara Gordon, and even once said that the book isn't very interesting, for the story doesn't relate to the real world in any sort of way. Also, prior to recoloring the book for a re-release in 2008, Bolland had admitted the end result wasn't quite what he had hoped, saying the story doesn't quite live up to Moore's previous works.

Well gentlemen, we respectfully disagree.

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Did you secure tickets for the one-night-only theater showing of The Killing Joke, or are you waiting for the DVD release? What's your favorite Joker story of all time? Sound off in the comments.

Batman: The Killing Joke hits the big screen on July 25th, 2016.