11 years ago, the fictional city of Gotham started spilling into our real world. The Bat Signal appeared on the sides of buildings. Supporters of Harvey Dent took to the streets ahead of an election for Gotham's District Attorney. An underground "Citizens For Batman" group was formed per instructions received via pizza deliveries from Gotham City Pizzeria. But while Gotham's white and dark knights gathered their followings, another formed under the banner of one name and one distinctive red-lipped smirk.
At that summer's Comic-Con International in San Diego, clues found on vandalized (or "Jokerized") dollar bills led attendees to a location from which they could watch skywritten laughter and a phone number appear in the sky. They were then sent to bowling alleys and bakeries where more clues could be discovered, stuffed inside bowling ball bags and baked into special cakes. Joker playing cards were scattered at random comic book stores carrying the address to a "Harvey Dent For District Attorney" campaign website. Eventually, the site's photo of the DA-hopeful was mysteriously disfigured by black eyes and a red grin, and some fans found a way to dismantle the image, pixel by pixel, until a new face was revealed underneath Dent's: Heath Ledger as the Joker.
This was actually the first image of Ledger's Joker that was released to the public. No boring press release. No grainy, leaked photo on social media. Fans had to devote their own time and energy into playing the Joker's game, just to get a look at him. Months before the follow-up to Christopher Nolan's Batman Begins was released, eager movie-goers had already formed an intimate investment in the character, and the stage for his and Batman's battle for Harvey Dent's soul was set.
This heroically elaborate "transmedia" marketing campaign was proof of just how much pressure The Dark Knight had on it to succeed. In 2008, Batman movies still had a lot to prove after the Schumacher era. Batman Begins had only been a moderate success at the box office -- earning about $40 million less than Tim Burton's Batman -- and the commercial failure of Bryan Singer's Superman Returns two years earlier left almost the entire weight of DC's cinematic canon squarely on Nolan's shoulders.
Even without the legacy of Jack Nicholson's beloved performance hanging over him, Ledger's casting -- as Joker-branded crazy as it seems now -- was highly controversial when it was announced in 2006. Fans were dismayed that the likes of comedic character actors like Johnny Depp and Robin Williams had been passed over; attacking Ledger's "pretty boy" looks and accusing him of having "the charisma of a lettuce leaf." His previous role in Brokeback Mountain meant some of the criticism had a nasty homophobic streak, too.