Other mistake: When Charles is buying the car, he says to the dealer, who knows Charles very well, that the phone should be on the left, and the dealer, who knows what's coming, says of course, and agrees that it must be done before delivery tonight. When the car arrives, the phone is still on the right.
Continuity mistake: Ingrid Bergman is sitting in the foyer of the hotel she is staying in. She orders a martini, which arrives pronto, but in the first shot, she picks up the drink and has a sip, and in the second shot, she isn't holding the glass anymore.
Continuity mistake: Rex Harrison is the first to buy the yellow car, but he asks for three changes, the first is to move the intercom phone to the left, but when George C Scott buys the car, the phone is on the right side, not the left.
Audio problem: When Rex Harrison and his wife come back from a drive in the new car, a man is winding the record player so it will play the record, but as he winds, the player moves, which would surely make the record jump, but it doesn't - the sound is perfect.
Continuity mistake: When Shirley Maclaine goes swimming in the blue lagoon, her hair is all wet before she enters the cave, but once in the cave her hair is only wet on the ends.