One thing about Frank Morgan and that role is he played SIX different characters!
Wiki:
Morgan is best remembered for his performance in
The Wizard of Oz (1939), in which picture he played a total of
six roles, most notably
the Wizard, which included the carnival huckster "Professor Marvel", the gatekeeper at the Emerald City, the coachman of the carriage drawn by "The Horse of a Different Color", the Emerald City guard (who initially refuses to let Dorothy and her friends in to see the Wizard), and the Wizard's scary face projection. Morgan was cast in the role on September 22, 1938.
W. C. Fields was originally chosen for the part of the Wizard, but the studio ran out of patience after protracted haggling over his fee.
I guess the Screen Actor's Guild wasn't too powerful back then! LOL.