 Moss Hart and George S. Kaufman, who wrote the play the movie is  based on, were good friends with Alexander Woollcott, a famous  critic, radio personality, and lecturer at the time. Woollcott  requested that they write a play FOR him, but they never came up  with a plot. One day Woollcott came to visit Hart unexpectedly and  turned his house upside down, taking over the master bedroom,  ordering Harts staff around and making a general pain of himself.  When Hart told Kaufman of the visit he said "imagine what would have  happened if he broke his leg and had to stay." They looked at each  other and knew they had a play.