One of the great indications of the success of Christopher Nolan's version of the Joker in The Dark Knight is how much he's talked about a whole decade after he debuted on screen. Still classed as one of the greatest comic book movie performances ever, the Clown Prince Of Crime earned Heath Ledger an Oscar (an unprecedented achievement for the genre) and is still the benchmark for movie villains. It's also the weight that will hang around every actor who dares try and play the Joker's necks.
The performance is underpinned by mystery and an identity crisis that only appears to be resolved when he comes face to face with Batman and has his "you complete me" epiphany. And that mystery is precisely why there are so many theories seeking to define him, despite the obvious fact that he doesn't want to be defined.
But for that precise reason, there might be one theory that actually answers the identity question best. What if his desire to remain anonymous is, in fact, PART of his identity? What if it's part of his job? What if he was actually a spy?
The logical place to start is a theory that's been going around for a long time: that the Joker is a Gulf War veteran...
5. The War Veteran Theory
One of the most popular theories about Ledger's Joker suggests that he is a former soldier suffering with PTSD, which would explain both his tactical nouse and his aptitude for weaponry and combat (he's flawlessly able to perform the regimental gun routine during the police parade). He looks like he's experienced and his time at war could explain both his identity crisis and his desire to watch the world burn.
But it isn't enough to simply say that he's a war veteran - or even that he's an obvious PTSD sufferer. He might present the image of a man without a plan - a dog chasing cars - but the precision with which he crafts his plans are more than just tactical experience. Consider the way he uses Melvin White as bait to stop Batman interfering in the parade plot: the Joker, whoever he is, is a precision instrument whose plans took weeks - even months - to enact.
And anyone with even vague experience of PTSD - or anyone who has struggled with it - knows that condition and the Joker's meticulous plotting would not be easy bedfellows. He is a contradiction of what most people think he is: the idea of him being the product of something traumatic is no more than part of his great facade. Hell, he even tells us that by spinning the lies about his scars. There's something else going on here.
Plus, there are just too many specific details that point to something even more: that his service was clandestine and covert. That he was a spy, in other words...