For fans of comedian Gary Gulman, the actor’s brief cameo in a pivotal scene during director Todd Phillips’ Joker must come as a complete surprise. What’s even more surprising is that during his big scene, a bout of constant laughter was throwing Gulman’s act just a little off its game. An audience member with an off-beat sense of timing to their reaction to Gulman’s comedy set was to blame, and that someone, as it turns out, was none other than Arthur Fleck himself, actor Joaquin Phoenix.
Article source: https://www.cinemablend.com/news/2483333/how-joaquin-phoenixs-joker-threw-off-a-co-star-during-a-pivotal-scene