Christopher Nolan didn’t set out to make sequels. As the director of hit thrillers like Memento and Insomnia, his personal style never seemed to mesh with the idea of helming a mega-franchise. After reenvisioning the Caped Crusader with 2005’s Batman Begins, though, Nolan couldn’t stop thinking about how his version of Batman would respond to the introduction of The Joker.

The result was The Dark Knight, a hyper-real exploration of how chaos shakes up the mission of the righteous, complete with huge stars, incredible stunts, and an Oscar-winning performance by the late Heath Ledger. To revisit this landmark movie, which was released 10 years ago, here are 19 fascinating facts about The Dark Knight.

1. IT HAS MANY COMIC BOOK INSPIRATIONS.

While it doesn’t adapt any one specific story to the screen, The Dark Knight did draw inspiration from several specific Batman stories in the pages of DC Comics. When researching and writing the film, director Christopher Nolan and his brother, co-writer Jonathan Nolan, specifically went back to The Joker’s very first appearance in 1940’s Batman #1 in search of how best to introduce the character.

Co-writer David S. Goyer, himself a DC Comics contributor, also cites the classic stories The Long HalloweenThe Dark Knight Returns, and The Killing Joke as keys to his research, with elements from each making their way into the film.

2. THE JOKER ALSO HAD DIVERSE INSPIRATIONS.

In addition to classic Joker stories like The Killing Joke, Nolan and star Heath Ledger drew on a diverse array of influences both in and out of comics to craft the film’s version of the Clown Prince of Crime. Before attempting to write the character, the Nolan brothers revisited Fritz Lang’s classic film The Testament of Dr. Mabuse as a study in how to write supervillains.

As for Ledger, he famously locked himself away in a hotel room for weeks, experimenting with voices. And he mannerisms until he developed something he was satisfied with. Among his inspirations: Sex Pistols icons Johnny Rotten and Sid Vicious and the anarchist character Alex from Stanley Kubrick’s classic film A Clockwork Orange.

3. NOLAN WAS INITIALLY RELUCTANT TO MAKE A SEQUEL.

Nolan and Goyer had ideas for how a trilogy of films would happen, of course, but after Batman Begins hit big, Nolan instead went off to make magician drama The Prestige. Ultimately, the lure of telling a Joker story proved too enticing for Nolan to pass up, and he eventually re-teamed with Goyer to begin mapping out the story that would become The Dark Knight.

when was the dark knight released?
when was the dark knight released?

4. HEATH LEDGER WAS THE FIRST CHOICE TO PLAY THE JOKER.

Though other stars like Adrien Brody expressed an interest in playing the film’s key villain, Heath Ledger was the only name on Nolan’s wish list.

“When I heard he was interested in the Joker, there was never any doubt. You could just see it in his eyes,” Nolan told Newsweek. “People were a little baffled by the choice, it’s true. But I’ve never had such a simple decision as a director.”

5. YES, HEATH LEDGER REALLY DID KEEP A JOKER DIARY.

Because of the actor’s untimely death in January 2008, at the age of just 28, Ledger’s performance as The Joker has been somewhat mythologized by fans. So the idea that he kept a secret “Joker diary” while getting into character might sound apocryphal. In fact, Ledger really did make a diary while preparing to play the character.

It included various clipped art (Alex from A Clockwork Orange figures heavily), stylized notes, and even lines from the script recopied in his own handwriting. In 2013, Ledger’s father Kim revealed the diary in a documentary. And he noted that his son did immersive work like this for every role. But “really took it up a notch” for The Joker.

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