Many, including Fred Astaire, blamed director Francis Ford Coppola for cutting off Astaire's feet during filming of his dancing scenes, but it was Warner Bros. who decided, after the filming had been completed in 35mm, to convert the film to the wider 70mm and promote it as a "reserved-ticket roadshow attraction." This was achieved by cropping off the tops and bottoms of the film frame, including some shots of Astaire's footwork.
Because of its satire on racism, this popular 1947 Broadway musical was considered such a hot potato in Hollywood that studios would not touch it unless they were allowed to change the story. Its original creators, E.Y. Harburg, Burton Lane, and Fred Saidy held out, and by 1968 it was able to be filmed with very few changes.
According to the commentary track on the DVD, choreographer Hermes Pan was fired part way through production because Francis Ford Coppola felt his choreography was too old-fashioned. Pan was replaced by the much younger choreographer, Claude Thompson, who was familiar to many of the dancers in the film. Pan was chosen because of his long association with Fred Astaire, having choreographed most of his most famous film musicals in the 30s and 40s.
The character of Billboard Rawkins, the racist senator, was based/suggested on the real-life Sen. Theodore Bilbo of Mississippi, who died while the show was being written.
During Howard's job interview at the Senator's mansion, Buzz keeps calling Howard 'George'. This is a reference to the Pullman Railway Car Company, which hired only African-American men as porters and required each of them to answer to the name 'George' while on duty. The company became known for its degrading treatment of its black employees, leading them to form the first all-black union in the United States.