When Edward G. Robinson says, "Revenons a nos moutons," he is using a French catch-phrase that literally means "Let's get back to the sheep" and is used to mean "Let's get back to the point at hand." The phrase comes from the French play "La Farce de Maitre Pathelin," in which a legal case about sheep keeps getting sidetracked in comical ways, and the judge has to keep saying it.
One of the photos in producer Ricardo Cortez's office is that of character comedian Edward Everett Horton.
The "meller" in the newspaper story at the film's opening is stage slang for "melodrama.
When Louis Calhern says, "The wish was father to the thought," he is quoting Shakespeare's Henry IV, Part 2.