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

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

Filmed on standing sets left over from _Cafe Metropole (1937)_ with 'Tyrone Power (I)' and Loretta Young.

Oscar Levant, who composed the opera in the film would later act in such films as Humoresque, Romance on the High Seas, and The Bandwagon.

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.

The Mephistopheles costume from "Faust" worn in the film was originally made for Lawrence Tibbett to wear in "Metropolitan" (1936).

The sixteenth of forty-seven Charlie Chan movies starring Warner Oland.

The unique billing listed Warner Oland vs. Boris Karloff above the title. Karloff had turned down the title role in Werewolf of London, which would have pitted him against his current co-star. The part was ultimately played by Henry Hull.

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