A Night at the Opera (1935)

Visible crew/equipment: When Groucho enters the rehearsal area, the shadow of the camera is visible behind him.

rabid anarchist

Continuity mistake: In the scene where Harpo is climbing out of the brig and goes to the open window of the famous aviators, he is shown climbing in the room from the outside with the rope he's climbing on draped across his chest. When he gets into the room the rope has disappeared!

Deliberate mistake: Riccardo is a stowaway on the ship, but he was standing on the dock when it pulled away.

rabid anarchist

Otis B. Driftwood: That's the fire escape. And, uh... that's a table, and this is a room, and there's the door leading out, and I wish you'd use it, I... I vant to be alone.
Henderson: You'll be alone when I throw you in jail.
Otis B. Driftwood: Isn't there a song like that, Henderson?

Otis B. Driftwood: Signor Lassparri comes from a very famous family. His mother was a well-known bass singer. His father was the first man to stuff spaghetti with bicarbonate of soda, thus causing and curing indigestion at the same time.

Otis B. Driftwood: You see that spaghetti? Now, behind that spaghetti is none other than Herman Gottlieb, director of the New York Opera Company. Do you follow me?
Mrs. Claypool: Yes.
Otis B. Driftwood: Well stop following me or I'll have you arrested.