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.
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.
The trivia item below may give away important plot points.
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.