Exactly what Arthur Fleck's plot or story in Joker 2 will be remains unclear, but introducing Harley in a manner similar to her role in "Joker's Favor" would create a great narrative conduit for her arrival as Arthur's literal partner in crime. The implications of Joker 2's musical story also add to how the film can embellish on the Joker's plot in "Joker's Favor". With the basic idea of Joker and Harley being out to eliminate a high-level target, whether, in the GCPD or someone else, a whole new spin could be put on it with the film's musical numbers and the absence of Batman.

Harley herself would also reshape the focus of both Joker 2 and "Joker's Favor" with the rumor that the film will take place from her perspective. Adapting Harley Quinn's origin as a character into a literal Harley origin story told through her own eyes in Joker 2 would be one further way that the film could adapt "Joker's Favor" for its purposes. With Joker 2 potentially altering the Joker-Harley romance in certain key aspects, such an origin could also show the madness of the pair, with Harley's insanity brought on, as always, by her relationship with Mr. J. Joker made clear that the stories about The Clown Prince of Crime that director Todd Phillips aims to tell are a far cry from more typical comic book movies. Still, that does not rule out adapting elements of the Joker and Harley Quinn's backstories in both comics and animation. "Joker's Favor" is exactly the kind of story that would fit Joker: Folie à Deux perfectly.