Continuity mistake: In the scene where a drunk Connor visits CK Dexter Haven at his home after Uncle Willie's party, Dexter's pyjamas and dressing gown change from shot to shot. First his pyjama top is done up, then it is open, then done up, then open again.
Revealing mistake: In the scene where Cary Grant punches Jimmy Stewart: Jimmy starts falling back (and you hear the sound effect of the punch) when Cary's fist is a good 1-2 feet from Jimmy's face.
Continuity mistake: Uncle Willy pours a glass just over half way full of vodka. With each shot the amount of vodka in the glass changes.
Character mistake: When Tracy is about to announce that the wedding is off, she turns to Dexter for help, and he says "Two years ago..." Tracy starts the announcement "Three years ago..."