Joker: Folie à Deux' actor Harry Lawtey told 'Variety' that he and Joaquin Phoenix pranked Lawtey's mother by having Phoenix appear on their FaceTime call while wearing his full Joker makeup. "I said,

Christian Bale's voice as Batman in the "Dark Knight" trilogy is infamous - and infamously bad for the vocal cords - but as it turns out, Joaquin Phoenix's unhinged laugh as Arthur Fleck in the "Joker" films was also a bit of a health hazard.

So, according to the Joker 2 team, their film isn't a musical, but is instead a film where the main characters break into song to describe their feelings when spoken dialogue isn't enough. And also, the characters sing like they would exist in the world of the movie, not on a Broadway stage.

Folie à Deux does have quite a few scenes featuring music, Lady Gaga, who plays Harley Quinn, doesn't think of it as a musical at all.

Joaquin Phoenix’s Joker will make his big screen return alongside Lady Gaga. Not long after Joker director Todd Phillips confirmed he would be writing and directing a sequel, Gaga confirmed her casting by sharing a video of her and Phoenix’s silhouettes dancing via Instagram.

Folie à Deux, recalled the time he and Joaquin Phoenix played a trick on Lawtey’s mom on the movie set. Phoenix stayed in full Joker makeup on set, even when not filming, so Lawtey said the actor played a trick on his unsuspecting mom.