The Man Who Knew Too Much (1956)

Visible crew/equipment: When James Stewart tells Doris Day that he lied about the telephone call being from the hotel, Doris gets excited and James struggles with her on the bed. During that scene, you can see on the upper left corner a shadow of a microphone.

Continuity mistake: Although the assassin and the ambassador are seated in the same tier of boxes, the assassin's view of his target through the opera glasses is from below and not from across.

Continuity mistake: Dr. McKenna is wearing a blue suit and hat during the bus ride in the beginning of the movie and then again as the family board the wagon and set out for their hotel. When the wagon arrives at their hotel and everyone gets out, McKenna's suit and hat have suddenly switched to light gray.

Trivia: Alfred Hitchcock makes his regular cameo watching a group of street entertainers.

James Warrender

Trivia: The conductor in the symphony scene is Bernard Herrmann, who is actually playing himself. His name is seen on a poster outside the theater. Herrmann composed the music for many of Hitchcock's films, including some of the score for this one.

raywest

Edward Drayton: Remember, you will only have time for just one shot. If you need another, the risk is yours.
Rien: I don't take risks.

Jo McKenna: So, what do you do?
Louis Bernard: I buy and sell.
Jo McKenna: I see. And what do you buy and sell?
Louis Bernard: Whatever gives the most profit.