The Dark Knight is widely considered one of the greatest comic book movies ever and regularly ranks toward the top in fan polls about the greatest movies, period. Part of the reverence for the film revolves around the legendary performance of Heath Ledger, who passed away before the release of the film that earned him an Oscar. It's well known that Ledger's commitment to the iconic role was complete down to the way he famously kept a Joker diary while developing the character in isolation. Today, we look through the history of his performance, and investigate ten things that most fans don't know about his role in the movie.

10 Heath Ledger was the only actor offered the role.

The arrival of Gotham's Clown Prince of Crime was teased at the end of Batman Begins, Christopher Nolan's well-received reboot of the Caped Crusader. Several actors pursued the role. Adrien Brody admitted to MTV News that he'd chased after it. Steve Carell went public with his Joker ambitions. The late Robin Williams, who worked with Nolan on Insomnia, was another actor whose name was tossed around. But the director has gone on record that Heath Ledger was the only actor he wanted, saying he offered him the role before The Dark Knight script was even finished.

9 Fans were upset with Heath Ledger's casting.

Heath Ledger's portrayal of the Joker is legendary. It cast a long shadow over anyone who dared to take on the role in Ledger's wake, including actor and 30 Seconds To Mars frontman Jared Leto, whose Joker earned mixed reactions. But once upon a time, the Internet was full of outrage over Ledger's casting, with a level of upset, confusion, and fury to rival the kind that met news of Ben Affleck's casting as the Dark Knight in what became Batman v. Superman: Dawn of Justice. One Redditor wrote that, "Heath Ledger has the charisma of a lettuce leaf." Narrow-minded fans had trouble envisioning the star of 10 Things I Hate About You and A Knight's Tale in the role, but smarter cinephiles were at least intrigued. After all, Ledger earned an Academy Award nomination for his work in Brokeback Mountain.

8 Jack Nicholson was pretty upset, too.

Jack Nicholson played The Joker in Tim Burton's Batman, the 1989 film from the Beetlejuice director that was the first of its kind to embrace the darker brooding version of the hero depicted in comics like Frank Miller's The Dark Knight Returns. While Nicholson's Joker was killed off at the end of Batman, there was talk of bringing him back, along with the rest of Batman's Rogue's Gallery, in a fear-gas induced sequence in what would have been the fifth installment of the franchise, featuring the Scarecrow as the main villain, and directed by Joel Schumacher. But the poor reception to the filmmaker's Batman & Robin sent the studio down the path toward a reboot. In a November 2007 interview with MTV News, Nicholson admitted he was "furious" when he learned another actor had been cast as the Joker in a Batman movie without anyone consulting him first. Around the same time, Ledger told film reporter Joe McCabe that he would have never sought to compete with Nicholson. "If Tim Burton was doing The Dark Knight and asked me to play the Joker I wouldn't have taken it. Because to try and even touch what Jack Nicholson did in Tim Burton's world would be a crime," he said. "I knew how Chris was. He had already set up the world for me. I'd seen what world it was that I would be playing in. So I knew it was open for a fresh interpretation. I also instantly kind of had something up my sleeve."

7 Heath Ledger's Joker owes much to Great Britain.

Ledger was born and raised in Australia but the disparate influences he cobbled together, reshaped, and forged into a never before seen Joker of his own creation were largely British in origin. The Joker's swagger came The Sex Pistols Sid Vicious, with a bit of Alex from Stanley Kubrick's A Clockwork Orange. The clothes of Vicious' band mate Johnny Rotten and designer Vivienne Westwood were also inspirations. The Joker first appeared in 1940's Batman #1 a year after the Caped Crusader's own debut in Detective Comics. He was the work of Batman co-creators Bob Kane and Bill Finger along with artist Jerry Robinson. While all three of those guys were Americans, Ledger's go-to Joker books were written nearly 50 years later by guys born in the UK. He cited 1988's Batman: The Killing Joke, written by English comics legend Alan Moore, and the following year's graphic novel Arkham Asylum: A Serious House on Serious Earth, by Scottish writer and illustrator Grant Morrison.

6 You wanna know how he got those scars?

Those mysterious scars are based on something from real life called the Glasgow Smile, or the Chelsea Grin, a violent mark left with a knife or broken glass, or some other sharp object. The gruesome practice reportedly originated in Scotland and was popularized on the streets of London by different gangs, like the hooligans of the Chelsea Headhunters. Of course the Joker never revealed how he got those scars. But we do know that prosthetics supervisor Conor O'Sullivan met a deliveryman with a Chelsea Grin and worked up the courage to ask him about it. The man allowed him to take photos. It was Nolan who suggested Ledger take a look at A Clockwork Orange as well as some of the paintings of Lord Francis Bacon, which partly inspired the makeup. Ledger worked on ideas with cheap drug store makeup as he developed his take on the character. With input from Ledger and Nolan, makeup artist John Caglione came up with the finished product, which earned him an Oscar nomination for Best Makeup.

5 The bank robbery scene is slightly out of focus.

The bank robbery scene was the first thing Nolan shot with Ledger. It was also the first full scene shown to film critics and reporters during the pre promotion for the film. Nolan realized while looking at the dailies that some of the shots were blurry. They reshot the whole scene, but the director liked Ledger's first pass so much, he decided to use that one in the finished film instead, slightly blurry shots and all.

4 Heath Ledger rode a skateboard around the set.

Ledger went method for the development of his take on the Joker, famously locking himself away in a hotel room for long periods of isolation, and keeping a twisted diary. But he didn't stay in character between takes. His makeup artist said he'd hug the crew at the beginning and end of each day and skateboard around the set. He'd often pull out his Joker journal when it was time to get back into character.

3 Michael Caine was so terrified of the Joker, he forgot his lines.

Ledger only did the voice and the laugh when the cameras were rolling, according to Christian Bale. This meant that he wasn't going "full-on Joker" during rehearsals, either. So when it came time to shoot, several of the actors were unsettled by his performance. Michael Caine said he was so startled by the Joker when he emerged from the elevator at Bruce Wayne's penthouse, the seasoned actor forgot his lines.

2 The Joker took an actual beating in the interrogation scene.

Both Christian Bale and Christopher Nolan have spoken about Heath Ledger's total commitment, particularly in the interrogation scene, which was the first thing the two actors shot together. Ledger kept upping the ante, egging Bale on to hit him for real, and throwing himself around against the tiled walls. Nolan has been careful to point out that the violence was carefully choreographed, but the impacts were real.

1 The actor twice directed the Joker himself.

Ledger was a budding director himself, with a few music videos under his belt, including a clip for Modest Mouse that was released after his death. He had spoken about making a documentary about English singer-songwriter Nick Drake, who overdosed on antidepressants at age 26 in the early 1970s. He'd planned to make his feature film directorial debut with an adaptation of The Queen's Gambit, a novel about a chess prodigy. Nolan was impressed enough with Ledger's directing work that he allowed him to helm both of the hostage videos made by the Joker in the film.