Trivia about Birds of Prey (And the Fantabulous Emancipation of One Harley Quinn).
- Cathy Yan is the first Asian woman to direct a superhero movie. She is second woman to direct a DC film after Patty Jenkins.
- Being produced under the working title of 'Fox Force Five'. Fox Force Five was the name of a fictional television show that never made it past the production of its pilot in the movie Pulp Fiction.
- Lady Gaga was offered the lead role of either Huntress or Black Canary, but she turned it down.
- Before Ewan McGregor was cast as Black Mask, Sharlto Copley and Sam Rockwell were considered to play Black Mask. Rockwell passed on the role, but was considered the "archetype" for the casting.
- Sam Rockwell was the archetype for Black Mask, but he became unavailable for the film.
- In the comics, Barbara Gordon was one of the founding members of the Birds of Prey, both as Oracle and later as Batgirl in the New 52 reboot. While she doesn't appear in the film, Cassandra Cain who served as Batgirl in the comics for a time prior to the New 52 reboot does appear in the film.
- Both Margot Robbie and Mary Elizabeth Winstead worked with Will Smith. Robbie was in Focus and Winstead was in Gemini Man.
- Both Lady Shiva and Katana were rumoured to be in the film. Karen Fukuhara would have reprised her role as Katana from Suicide Squad.
- Before Jurnee Smollett-Bell was cast, Gugu Mbatha-Raw and Janelle Monae were rumored to be in the running for Black Canary. Previously, Vanessa Kirby, Jodie Comer and Blake Lively were rumored as well.
- Before Mary Elizabeth Winstead was cast, Cristin Milioti, Margaret Qualley and Sofia Boutella were rumored to be in the running for the role of Huntress. Previously, Alexandra Daddario had been rumored as well.
- In the Birds of Prey comics, Harley Quinn has never been a member of the team.
- David Cain was rumoured to be the villain of the film.
- Peyton Elizabeth Lee was rumored for the role of Cassandra Cain.
- This is the second time that both Ewan McGregor and Mary Elizabeth Winstead are working together after Fargo.
- Throught they played mother and daughter in the film, Charlene Amoia is 8 years older than Mary Elizabeth Winstead in real life.
- In the Birds of Prey comics, neither Harley Quinn nor Cassandra Cain have been members of the eponymous team.
- In the comics, Barbara Gordon was one of the founding members of the Birds of Prey, both as Oracle and later as Batgirl in the New 52 reboot. While she doesn't appear in the film, Cassandra Cain who served as Batgirl in the comics for a time prior to the New 52 reboot does appear in the film.
- Both Jurnee Smollett-Bell and Ella Jay Basco were in at least one Grey's Anatomy episode.
- Kristen Stewart was the studio main choice for the role of Barbara Gordon/Batgirl before the character was cut from the script.
- Although it has yet to be confirmed by the filmmakers, Jared Leto has teased on his instagram that he'll be reprising his role the Joker.
- It has been rumored that Birds of Prey will be the first movie of a "Harley Quinn Trilogy". The second and third movies in the trilogy are rumored to be Gotham City Sirens and Birds of Prey vs. Gotham City Sirens, respectively.
- Birds of Prey features two cop characters that are named after Bruce Timm and Paul Dini. Timm was the Co-creator of Batman the Animated Series and is an artist for DC comics and Paul Dini is the creator of Harley Quinn.