Beautiful Girl

A strange scene. How many other musical numbers can you think of that were set in a bathroom? Bing goes in and half closes the door and Sterling Hollaway sticks the mike through the opening. At one point, he opens the door a bit wider and peeks in and gawks. What was that about? Bing finishes the song in tune and in tempo: "and I forget the words. So this will have to do". Was that in the script or an ad lib they kept in?