Ringo Starr's character Youngman wasn't in the original book. The part was written especially for him, with many of Guy's early exploits adapted as Youngman's.
After watching rushes from the first day of filming, Peter Sellers leaped to his feet and said "Thank God we caught it in time!" He felt his performance was so bad that the film should be canceled. He was eventually persuaded to continue.
During the filming of scenes with the topless "slave" girls rowing the ship, the actors kept deliberately flubbing their lines just so they could watch the girls.
Final film of Isabel Jeans.
First film acting role of Graham Chapman.
Grand refers disparagingly to prospective "Magic Christian" passengers Simon and Deborah Devonshire as being "hardly Burke's"; a reference to "Burke's Peerage, Baronetage & Knightage", an authoritative genealogy guide to British blue-blood families.
In the promotional poster for the movie Fletch, one of Irwin Fletcher (Chevy Chase)'s alter egos is a basketball player named "Magic Christian".
Many of the Central London exterior and building shots were filmed in and around Westminster School, London.
Sellers wanted to film the final scene, of the vat of manure, at the base of the Statue of Liberty. Sellers, Starr, their families, entourage, and some of the film's production team traveled to New York on the luxury liner Queen Elizabeth 2. John Lennon and Yoko Ono hoped to join them and travel to the United States, but were not allowed, due to Lennon's being denied a US visa (lookalikes were filmed boarding instead). The footage at the Statue of Liberty was not used, and no filming was done on the ship.
The movie's theme song "Come And Get It" was written and produced by Paul McCartney.
The role of Youngman Grand was originally offered to John Lennon, who was tempted to perform the role but eventually had to decline due to legal difficulties related to his October, 1968 arrest for possession of marijuana. Lennon's Beatles band mate Ringo Starr - who was hoping to pursue a career as an actor after having received favorable reviews for his performance in the 1964 Beatles film A Hard Day's Night - stepped into the role intended for Lennon.
Two of the writers were John Cleese and Graham Chapman of Monty Python fame. The Python sketch "The Mouse Problem" was written for this movie, but was rejected by Peter Sellers.