Crowe agreed to do the movie in return for RZA giving some rap lessons to the South Sydney Rabbitohs, a rugby league team he co-owns.

The first cut of the film was four hours long. RZA suggested splitting it into two films, but producer Eli Roth disagreed, and it was ultimately cut down to approximately 90 minutes.

RZA and Eli Roth worked on the screenplay together over two years, talking through every aspect of the story, down to the detail of every weapon.

Byron Mann was initially intended for the role of Poison Dagger, but when the actor who was to play Silver Lion dropped out of the production shortly before shooting, Mann was recast. Many of Silver Lion's attributes, including his psychopathic nature, were originally developed by Mann for the other role.

Donnie Yen was turned down the role of Poison Dagger.

RZA wrote the role specifically for himself, and trained in Hung Ga for 1-2 hours a day over 2 months in preparation.

Liu wanted to emphasize Blossom's strength against all the male fighters and convinced RZA to give the character a fight sequence with Cung Le's Bronze Lion.

The Abbott, played by Gordon Liu, is the same character referred to by Bill in Kill Bill: Vol 2 as he recounts 'The Legend of Pei Mei' to "The Bride" around the camp fire. He is the ancestor of "The Bride"'s master in Kill Bill.

The character was partly inspired by RZA's late cousin Ol' Dirty Bastard. Crowe based his performance on Clint Eastwood in Dirty Harry (1971) and The Outlaw Josey Wales (1976). Crowe agreed to join the cast because of his previous working relationship with RZA. Crowe was only able to spend 10 days filming his scenes.

Crowe and Le were originally scripted to fight each other, but because of Crowe's limited shooting schedule, he did not have the time to rehearse the fight, and instead Le was scripted to fight Liu.

The song sung in the brothel early in the film is the same song heard at the beginning of The Killer (1989).

RZA said that he had Yune in mind for the role before the script had been completed.

Rick Yune and Dave Bautista, who are adversaries in this movie, both played villains in separate James Bond movies; Yune in Die Another Day (2002) and Bautista in Spectre (2015).

WILHELM SCREAM: As Thaddeus throws a man from the balcony.

Liu's role was written for RZA's Shaolin teacher Shi Yan Ming, but Ming could not obtain permission to return to China for filming.

As Thaddeus is seen moulding his new fists, the voice of The Abbott is heard in a flashback to his Buddhist monk training, saying: "In the beginning was the Word." This is likely a quote from John 1, as RZA has studied multiple religions including Christianity, Buddhism and Islam, and has stated that The Bible, The Qu'ran and the Lotus Sutra are three of his favourite books.