Daffy Duck in Hollywood (1938)

Continuity mistake: Von Hamburger has no buttons on his shirt from the start of the cartoon, but when he is watching his completed film and taking a deep breath, buttons have suddenly appeared.

Von Hamburger: This should be a close-up, am I r-r-r-r-r-right, boys?
Assistant Directors: Yes, sir, yes, sir, yes, sir, yes, sir.