From Who the Devil Made It: Conversations with Legendary Film Directors, by Peter Bogdanovich
By the end of the film, would you say that [Cary] Grant has abandoned his scientific life?
Well, let’s say he mixed it. He had an awfully good time and if anyone had to choose between the two girls, they’d certainly choose Hepburn. We start off, as I said, with a complete caricature of the man and then reduce it to give him a feeling of normality because he certainly wouldn’t have had any fun going through life the other way, would he? You’ve got a rather happy ending. You have to almost overdo it a little in the beginning and then he becomes more normal as the picture goes along, just by his association with the girl. Grant said, “I’m kind of dropping my characterization.” I said, “No, she’s having some influence on you. You’re getting a little normal.”