Harley Quinn vs. the Joker

Harley Quinn vs. the Joker is an unproduced American film based on the DC Comics characters Harley Quinn and Joker that was to be distributed by Warner Brothers. It was intended to be part of Warner Brothers' DC Extended Universe.

Plot
Harley kidnaps Dr. Phil, due to relationship complications with her and the Joker.

Development
Untitled Harley Quinn and Joker film: The film, with the working title Harley Quinn vs. the Joker, was announced with filmmaking duo Glenn Ficarra and John Requa attached as co-writers/-directors/-producers. By October 2018, the script was completed, and though the project was originally intended to begin production immediately after The Suicide Squad, the filmmakers have since stated that production would begin once filming on Birds of Prey has wrapped. By February 2019, the film had been cancelled.

Why It Was Cancelled

 * 1) Suicide Squad received negative reviews from critics and fans alike.

Result

 * The film was permanently cancelled.