Update 10/08: Joker cinematographer Lawrence Sher has given new context to the viral outtake of Joaquin Phoenix yelling at him on-set of the DC film, confirming, “it was a bit.”
In a recent interview with Business Insider, Sher (aka the “Larry” referenced in the Jimmy Kimmel clip) explained that the outburst was staged, as Phoenix wanted to pull a prank on director Todd Phillips by appearing to get into a verbal disagreement with a member of the crew.
“It was a bit. Joaquin is actually a super playful guy and loose,” Sher said, adding, “he’s such a good actor that nobody even got it on set. He played it too straight.”
Source: IGN.com Viral Joker Outtake of Joaquin Phoenix's Outburst Confirmed as Prank