Joaquin Phoenix threw himself into playing the Joker by losing so much weight he went mad.
The star lost around 52 pounds (24 kilograms) to play the part, which he has interpreted as a failed stand-up comedian turned criminal, and says shedding the weight made him lose himself psychologically.
"The first thing for us was the weightloss - I think that's really what I started with," he told The Hollywood Reporter at a Venice Film Festival press conference. "And, as it turns out, that then affects your psychology. You start to go mad when you lose that amount of weight in that amount of time.
"There's a book that I read about political assassins and would-be assassins that I thought was really interesting, and kind of breaks down the different types of personalities that do those sorts of things."
The DC Comics supervillain is an iconic role in comic book cinema, with Jack Nicholson and the late Heath Ledger both delivering acclaimed performances in the role. However, Joaquin insists he has not studied either interpretation - as he's determined to play the Joker in his own way.
"For me, the attraction to make this film and this character was that we were going to approach it in our own way," he mused. "So for me, I didn't refer to past interpretations of the character."
Joker will debut in cinemas on 4 October.
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