4. The Wizard was supposed to have been portrayed by W. C. Fields
W. C. Fields was at the height of his powers as a radio star in 1939, and when Ed Wynn, a popular radio host, comedian, and actor of the day turned down the role of the Wizard/Professor Marvel, the producers turned to him. The comedian’s public persona as a charming charlatan and con man – one which Fields carefully cultivated throughout his career – was believed to be perfect for the two characters he was set to play. But Fields was also notorious throughout the film industry as being challenging to work with.
Fields argued with producers, directors, and writers (as well as fellow actors) over scripts, storylines, timing, and virtually all other aspects of filmmaking. He frequently used ad-libs while filming scenes and then refused to submit to a retake. Fields demanded a salary which MGM considered to be too high, especially when it was coupled with his penchant for being disruptive on the set. With Fields out, and shooting set to begin, MGM selected one of their stock players, Frank Morgan, for the title role in the film, and the script was once again rewritten.