Anglo/French actor Etienne Girardot, who plays the man who goes around the train holding "Repent!" signs, was the only actor from the original Broadway cast to appear in the film.

Columbia also had attempted to acquire the services of William Frawley, who played Jaffe sidekick Owen O'Malley on Broadway, but instead borrowed Roscoe Karns from Paramount.

The film's opening musical theme is the same waltz Columbia had used for its big screwball hit of the same year, It Happened One Night (1934).

Howard Hawks and Carole Lombard were second cousins.

Noted German actors Herman Bing and Lee Kohlmar have uncredited bits as Passion Players from Oberammergau.

Quotes from Twentieth Century:

"Now, before we begin I want you all to remember one thing. No matter what I may say... no matter what I may do on this stage during our work... I love you all." - Oscar Jaffe

"Get out of my theater, you gray rat! And don't have that fat wife of yours come around again, pleading for you!" - Oscar

"You squalling little amateur. On your feet! Get up! Take that hump out of your back. You're not demonstrating underwear anymore!" - Oscar

"What do you know about talent? What do you know about the theatre? What do you know about genius? What do you know about anything, you... bookkeeper!" - Oscar

"O.J., suppose - just hypothetically, of course - that you, Mr. Bromo, could get together again with Miss Seltzer." -- Oliver Webb

"Go on, Owen... tell her I'm dying... and DON'T OVERACT!" - Oscar

"I never thought I should sink so low as to become an actor!" - Oscar

"Yes, I tried to save you pain. I lied, yes, only to save you." - Lily Garland
"That's from Sappho!" - Oscar

"Oh, an artist!" - George Smith
"You're darned tooting I am!" - Lily

"Oscar, you're complete: the most horrible excuse for a human being that ever walked on two legs." - Lily

"Love blinded me. That was the trouble between us as producer and artist." - Oscar
"So that's what it was, was it? How about your name in electric lights bigger than everybody's, and your delusion that you were a Shakespeare and a Napoleon and a Grand Lama of Tibet all rolled into one?" - Lily

"Those movies you were in! It's sacrilege throwing you away on things like that. When I left that movie house, I felt some magnificent ruby had been thrown into a platter of lard." - Oscar

"To John Ringling: I'm in the market for 25 camels, several elephants, and an ibis... Give me the rock-bottom price." - Oscar

"That's the trouble with you, Oscar. With both of us. We're not people, we're lithographs. We don't know anything about love unless it's written and rehearsed. We're only real in between curtains." - Lily

"He won't shoot himself. It would please too many people." - Oliver Webb

"I close the iron door on you." - Oscar