The Dark Knight: Chilling theory adds twist to The Joker's past

Ever wondered where the Joker originated? Comedian and actor Patton Oswalt may have the answer.

Oswalt recently watched Christopher Nolan's 2008 film The Dark Knight, where Heath Ledger played the iconic villain, The Joker.

After watching the movie, Oswalt shared on Facebook his fan theory on how The Joker came to be his whacky, insane self.

Christian Bale stars as Batman and Heath Ledger as The Joker in The Dark Knight. Photo / Supplied

"I've always liked the theory that Heath Ledger's Joker in Christopher Nolan's Dark Knight is a war veteran suffering PTSD," Oswalt's post begins.

"His referencing a 'truckload of soldiers' getting blown up, his ease with military hardware, and his tactical ingenuity and precision planning all feel like an ex-Special Forces soldier returned stateside and dishing out payback.

"But I just rewatched The Dark Knight, and another wrinkle came to mind about The Joker.

"What if he's not only ex-military, but ex-military intelligence?

"Specifically — interrogation?," he continues.

Mind blown yet? Here's his reasoning.

"He seems to be very good at the kind of mind-f***ery that sustained, professional interrogation requires. His boast about how "I know the squealers" when he sees one. The way he adjusts his personality and methods depending on who he's talking to, and knowing EXACTLY the reaction he'll get: mocking Gamble's manhood; invoking terror to Brian, the "false" Batman; teasing the policeman's sense of loyalty to his fallen, fellow cops; digging into Gordon's isolation; appealing to Harvey Dent's hunger for 'fairness'," Oswalt writes.

Actor Patton Oswalt has delivered an intriguing theory about Heath Ledger's Joker character in The Dark Knight. Photo / Supplied

"He even conducts a 'reverse interrogation' with Batman when he's in the box at the police station — wanting to see how 'far' Batman will go, trying to make him break his 'one rule.'

"He constantly changes his backstory (and thus who he is). To Gamble and his henchmen, he's an abused child (figuring that they were also the products of abuse and neglect). To Rachel, he's a man mourning a tragic love — something she's also wrestling with."

Oswalt concluded his theory explaining the way The Joker said his final goodbye to Batman, saying their relationship is "irresistible force meeting an immovable object", is something an interrogator would say after an interrogation.