While filming, Donna Reed (who plays Mary Hatch) said that she came from a country background and that living in a small town like Bedford Falls would be second nature for her. Lionel Barrymore (who plays Mr. Potter) bet Reed $50 that she couldn't milk a cow. She won the bet with no problem. (Source)

The guy who played Mary's date at the dance was Carl Switzer, who played Alfalfa in the original Little Rascals. That retractable dance floor with a swimming pool under it still exists at Beverly Hills High School. Take that up at your next student government meeting. (Source)

During the scene where Mary breaks a window in the abandoned house so she can make a wish, Frank Capra had a marksman on hand to shoot out the window. He wasn't needed: Donna Reed successfully smashed it on the first attempt. Is there anything that woman couldn't do? (Source)

During the phone call scene where George and Mary first kiss, Jimmy Stewart was pretty nervous. He hadn't kissed a woman since he came home from the Army. He apparently got in the mood, however. The Hays Code censors cut part of the scene because the embrace was considered a little too steamy. (Source)