Roman Holiday (1953)

Continuity mistake: When Audrey and Gregory are saying goodbye in the car, there are two shots where rain is visible outside the car window behind them. When Audrey gets out and walks away, however, it's dry outside.

Princess Ann: What do you sell?
Joe Bradley: Er, fertilizer.

Trivia: When Gregory Peck puts his hand into the Mouth of Truth and withdraws it (hand tucked into sleeve) the scream that Audrey gives is real. The prank was unscripted, but the reaction so perfect that it was left in.