Factual error: Since it's cold and snowing throughout most of the movie, how come you never see the people's breath? This is because when they filmed these parts, it was very hot outside, but it's still a mistake.
Suggested correction:Seeing a person's breath is not entirely dependent on how cold it is, but rather how much or how little humidity there is in the air.
Seeing your breath is based on how cold it is, however, with high enough relative humidity, you're able to see your breath in warmer temperatures. If it's cold enough to snow, it's cold enough to see your breath, regardless of what the humidity is.
Continuity mistake: When George crashes his car into the tree, the front of the vehicle is against the tree, but the next shot of George exiting the car shows the vehicle off to the side of the tree.
George Bailey: Just a minute... Just a minute. Now, hold on, Mr. Potter. You're right when you say my father was no businessman. I know that. Why he ever started this cheap, penny-ante Building and Loan, I'll never know. But neither you nor anyone else can say anything against his character, because his whole life was... Why, in the 25 years since he and his brother, Uncle Billy, started this thing, he never once thought of himself. Isn't that right, Uncle Billy? He didn't save enough money to send Harry away to college, let alone me. But he did help a few people get out of your slums, Mr. Potter, and what's wrong with that? Why... Here, you're all businessmen here. Doesn't it make them better citizens? Doesn't it make them better customers? You... You said...what'd you say a minute ago? They had to wait and save their money before they even ought to think of a decent home. Wait? Wait for what? Until their children grow up and leave them? Until they're so old and broken down that they... Do you know how long it takes a working man to save $5,000? Just remember this, Mr. Potter, that this rabble you're talking about...they do most of the working and paying and living and dying in this community. Well, is it too much to have them work and pay and live and die in a couple of decent rooms and a bath? Anyway, my father didn't think so. People were human beings to him. But to you, a warped, frustrated old man, they're cattle. Well in my book, my father died a much richer man than you'll ever be!
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."
