The Joker's true origins in The Dark Knight are unknown, but three famous theories can help solve the mystery. Contrary to what Tim Burton had done with Jack Nicholson's Joker in 1989, Nolan's The Dark Knight chose not to show how the Joker became the villain audiences know so well. More than avoiding showing the character's origins, The Dark Knight played with that mystery and had Heath Ledger's Joker telling different background stories to different people throughout the film.
While the comics have also always been dubious about the Joker's real origins, Alan Moore's groundbreaking The Killing Joke offered what, to this day, is the backstory most commonly associated with the character. In the graphic novel, the Joker remembers the tragedy of a failed comedian who agrees to participate in a robbery in order to support his family – only to later find out that his pregnant wife died in an accident and end the night by falling into a vat of acid. This heavily inspired the Joker's origins in Tim Burton's Batman, but The Dark Knight chose to skip the vat of acid idea from the start as Heath Ledger's Joker actually wore makeup instead of having a paled skin.
Nolan and Ledger reinvented the Joker for the big screen and crafted a version of the character that will forever be acclaimed. One of the instruments for that was to flip everything audiences thought they knew about the character, including his origins. To this day, the actual events that led to the birth of The Dark Knight's Joker are a mystery, one of the many in Nolan's career that he most likely will never explain. Still, even though the film deliberately portrays the Joker as some sort of force of nature with no specific origin, The Dark Knight leaves some clues that serve as fuel for theories on how Ledger's Joker actually got his scars - and how he became Gotham's worse nightmare.
The Joker Was An Arkham Patient During Batman Begins
This theory perfectly connects The Dark Knight with the events of Batman Begins. During the third act of Nolan's first Batman film, Ra's Al Ghul and the League of Shadows disperses Scarecrow's fear gas across the Narrows bay, setting up mayhem and destruction that nearly spread across the entire city. In addition to the toxin, the League of Shadows also set free all the highly dangerous criminals trapped in Arkham to cause even more panic among the citizens of Gotham. According to this theory, the Joker was one of the patients who were at Arkham that night.
Already having mental health conditions and now being exposed to Scarecrow's fear gas, the Joker would have entered a spiral of insanity that saw him "born" amidst the chaos of the Narrows. This theory would help explain the villain's obsession with Batman, as the caped crusader was soaring above the island that night. Batman Begins featured a couple of scenes showing how people affected by Scarecrow's fear toxin perceived Batman, and that may have been the image that stuck in the Joker's mind for a long time. It is worth remembering that, at the end of Batman Begins, the Joker was already starting to make a name for himself in Gotham. However, it was never clear how much time had passed between the film's final battle and the epilogue, meaning that this theory could still work.
The Joker Is A War Veteran
Perhaps the most popular theory for Heath Ledger's Joker origin is that he is a war veteran - more specifically, an ex-special forces - currently going through some form of PTSD. One of the first pieces of evidence for this theory is the fact that the Joker demonstrates expertise in the handling of different types of firearms, much more than would be expected from a simple criminal. Throughout the film, the Joker uses different types of weapons, from revolvers to RPGs. In addition, the Joker also demonstrates hand-to-hand fighting skills good enough to exchange a few hits with Batman, further supporting that he had some sort of training.
Heath Ledger's Joker had a very specific agenda against order and institutions, which could have been a consequence of a traumatic experience in the military. Throughout The Dark Knight, the Joker also demonstrates having experience in interrogation techniques, something he may have used or been a victim of in his time overseas. Another clue that supports this theory is the example the Joker uses to make his point about anarchy: if a truck full of soldiers explodes, no one panics because it is "all part of the plan". It is a very specific example, and it could be what really happened to the Joker. Besides this, if the Joker really was a special ops agent of some sort, that would help explain why there is no record of him in Gotham's database, as he could have been part of a mission that required his records be erased or made classified. Back home and traumatized, the Joker may have found himself struggling to fit into a society he no longer recognized, resulting in a subsequent breakdown that saw him take on his villain alias.
The Joker Is A Rogue Member Of The League Of Shadows
Another theory connecting the Joker to Batman Begins is that the villain is a former member of the League of Shadows. Analogously to the war veteran theory, this would explain why the Joker has combat and weaponry skills: he had training. Much like Bruce and Bane, the Joker would have been trained by Ra's Al Ghul to become an agent of the Shadows and help restore balance to doomed places. However, rather than judging the League's methods as too extreme as Bruce did or making the League's ideology his own as Bane did, the Joker would have flipped off Ra's Al Ghul's doctrine and become an agent of chaos instead of an agent of order. Another version of this theory goes to say that the Joker was one of the agents who were part of the League of Shadow's Scarecrow toxin attack in Batman Begins and that fighting Batman and being exposed to the gas was what drove him insane.
Each of these three theories helps explain one side of Heath Ledger's Joker. The truth is that the character was written in such a way that it is difficult to say what is real and what is an act about him. Whether Nolan ever came up with a true origin story for The Dark Knight's Joker will remain a mystery - but one that is still rife with exciting audience theories and speculation.
