Trivia

Benson Fong, who appears as an extra during the opera scenes, later returned to the series to play Tommy Chan, Charlie's #3 Son.

Though only excerpts are used, Oscar Levant wrote an entire short opera for this film.

Stage manager Maurice Cass vows that the opera will go on "even if Frankenstein walks in!" Audiences were well aware that this in-joke referred to star Boris Karloff, who was in the theater at the time.

Boris Karloff did not do his own singing in this film. His voice was dubbed by Tudor Williams.

The red cape used by Boris Karloff in this film was sold on December 16, 2011 for $19,000.00 + 4,370.00 buyer's premium + 8.25% sales taxes + shipping and quite possibly other added fees. A display mannequin made to Karloff's Gravelle character effigy came with the cape.