The musical starts with the busybody postman who reads everybody's mail, Hector (Walter Brennan), delivering mail to the Dana household and particularly to Cora (Helen Broderick), the maid who he is in love with. Professor Oliver Dana (Robert Benchley) is the head of the household. The oldest sister is Sylvia (Anne Gwynne), an actress, and the youngest is Nancy (Ann Gillis), who is a bit of a flirt and has all the boys fighting over her. The middle sister Jane (Deanna Durbin), the "nice girl", makes her entry singing the song "Perhaps" to the rabbits she takes care of. Her father is trying to write a book about diet and is testing it on rabbits. Don Webb (Robert Stack) is her boyfriend, an avid car buff.