In an odd way, the controversial casting of one Batman actor helped facilitate one of the longest-running and most popular Joker castings of all time. For many DC Comics viewers, the DC Animated Universe includes the definitive versions of many classic DC characters. Among the DCAU’s best castings are Susan Eisenberg’s Wonder Woman, the late Kevin Conroy’s Batman, and, of course, Mark Hamill’s Joker. Unsurprisingly, as both Batman’s nemesis and one of the superhero genre’s most iconic supervillains, The Joker has appeared in numerous Batman adaptations, with different iterations focusing on different aspects of the mirthful murderer.

Many consider Mark Hamill’s Joker to be the best iteration, and for good reason. Hamill’s Joker had the perfect balance of silliness and genuine horror, juxtaposing his madcap humor with surreal murders and the ruthlessness of a gritty old-fashioned gangster. Hamill’s version of Joker became so popular, in fact, that Hamill played the supervillain in many other properties and franchises outside of Batman: The Animated Series and the DCAU, such as the critically acclaimed Arkham video games. Fascinatingly, one of the most controversial – yet later beloved – Batman castings of another franchise, may have contributed to Hamill’s eventual casting as The Joker.

Fascinatingly, the casting of Michael Keaton as Batman had an influence on Mark Hamill’s audition for the Joker role. Hamill revealed in an interview with WIRED that he had doubts that the showrunners would hire the actor best known for playing Luke Skywalker in Star Wars as the Joker. Yet the controversial casting of Keaton in 1989’s Batman helped Hamill submit a calm and confident audition for the Joker role. Hamill stated:

I just read for it. I had a confidence that really helped me, because there was this big outcry that Michael Keaton was gonna play Batman. 'Oh, he's Mr. Mom, he's a comedy actor.' I mean, they hadn't even seen him [in the role] and they didn't realize how great he would become. But, there was great controversy.

Interestingly, Michael Keaton’s Batman casting was not the only way that the 1989 film influenced the DCAU. Batman: The Animated Series itself was created to be part of the marketing campaign for the film’s 1992 sequel – Batman Returns. Without Keaton’s Batman debut, there would be no Batman animated series and thus no DCAU.

Michael Keaton is one of the most popular Batman castings nowadays, but when he was initially announced as the star of the then-upcoming Batman film, there was widespread and well-publicized outcry from longtime readers of Batman comics. Many viewers worried that the film would be campy and comedic like the 1966 Batman TV series, and the announcement of Tim Burton (of Pee-wee's Big Adventure fame) as director and Michael Keaton, known for comedies like Mr. Mom and Beetlejuice, only worsened these fears. Prospective viewers also felt that Keaton did not have the physique for a comic-accurate Batman.

Of course, these fears were alleviated for many when the first teaser for Batman was released, and once the film arrived in theaters, the general opinion of Michael Keaton as Batman turned around completely. Keaton’s iteration of Batman brought a likable quirkiness and naturalism to the role that many likely did not expect. When wearing the Batman cowl, Keaton kept his dialogue to a minimum, letting his actions and expressions do most of the talking. By now, Keaton is, deservedly, considered one of the best actors to play Batman on film.

What Michael Keaton’s casting as Batman and Mark Hamill’s casting as The Joker proves is that an actor’s talent matters far more than the roles that they are best known for. Some of Keaton’s successors in the Batman role – particularly Ben Affleck and Robert Pattinson – were similarly controversial at first, but quickly won over viewers once their respective films were released. The same could be said for Hugh Jackman as Wolverine and Gal Gadot as Wonder Woman.

Batman, just like Joker, has been adapted to the screen a number of times over the last 60 years, and it's given a wide variety of actors the opportunity to offer a new interpretation of Bruce Wayne. While there might be backlash when an actor is first cast as Batman, just as there was with Keaton and Affleck and Pattinson, they've each brought something new to the Dark Knight. Hamill, meanwhile, has given an arguably definitive performance as the Joker, and it was all thanks to the confidence he gained from seeing Keaton be cast as Batman.

Without the controversy (and later success) of Keaton’s Batman casting, viewers would never have had arguably the best iteration of Joker in Batman: The Animated Series.