Joaquin Phoenix's performance as the Joker - in the new movie of the same name - has been praised by almost every critic lucky enough to see a preview of the long-awaited movie.
But the mercurial actor has said he went to new depths in order to get the character just right - including nailing the villain's iconic laugh.
Speaking to The Hollywood Reporter, the 44-year-old said it was 'almost painful' to hit the right note with the maniacal clown.
He said it needed to be 'something that's almost painful. I think for Joker it's a part of him that wants to emerge. I think we all kind of assume what a Joker laugh is and it felt like a new, fresh way of looking at it'.
"I didn't think that I could do it, I kind of practised alone but I asked Todd to come over to audition my laugh. I felt like I had to be able to do it on the spot and in front of somebody else. It was really uncomfortable. It took me a long time."
The film is an origins story, showing how downtrodden comic Arthur Fleck becomes the Joker.
But the cackle was just one component of the character Phoenix was trying to create during filming - which he said changed almost daily.
"He's so hard to define and you don't really want to define him," he said, claiming she decided not to attribute a specific mental health issue his character.
"We would get close at times where I found that I would identify certain parts of his personality or his motivation and then I would back away from that because I wanted there to be a mystery to the character.
"Throughout the course of shooting it felt like every day we were discovering new parts of his personality, up until the very last day."
And it seems that all that hard work and sacrifice was well worth it.
Ahead of its full release next month, the movie has already been a hit with critics with some even suggesting Phoenix might earn himself an Oscar nomination.
A five-star review in Empire said the origin-story was 'bold, devastating and utterly beautiful'.
Adding: "Todd Phillips and Joaquin Phoenix have not just reimagined one of the most iconic villains in cinema history but reimagined the comic book movie itself."
Director and writer Todd Phillips told the audience: "Why can't you do a genre comic-book film like that? We thought this could be an exciting approach to this genre. I'm not sure what it means for DC or Marvel...
"It was a hard movie for us to get made, to convince DC and the studio at first, but we thought we would keep pushing because we thought it would be special."
Joker hits cinemas on 4 October.