Trivia: During the scene where a drunken Uncle Billy walks home, a loud crashing sound is heard. The crashing sound was due to a crew member dropping a large tray of props. Thomas Mitchell quickly ad-libbed the line that he was all right. The crew member who dropped the tray was afraid he would be fired but instead director Frank Capra gave the crewman a ten dollar bonus for "improving the sound."
Trivia: At the end of the movie Lauren Bacall says to Marlowe "Phil, there's two men out back behind some trees". This is the only time in the movie that she refers to him by his first name. (01:49:45)
Trivia: Leopoldine Konstantin plays Claude Rains' mother in the movie, even though in real life she was only three years older than him.