Character mistake: When Lauren is playing roulette, she has $14,000 worth of chips sitting on red - if she wins, she gets double, $28,000; and if she loses, she loses all of the $14,000 - but the croupier is troubled and says to Lauren that she hasn't got enough to cover the bet, which is ridiculous; all her $14,000 chips are sitting on red, what more does she need? Even the head croupier is called in, and, after much chatting, all the other players are asked to take their chips away as only Lauren is playing this round, which is ridiculous: All they have to lose is $28,000; that's nothing for them.
Character mistake: In every scene George is with Mary, she never once wears glasses. However, when he meets her coming from the library after he was never born, she is wearing glasses. George is shown how he has influenced all the people in Bedford Falls over his lifetime, but having Mary's eyesight degrade to the point of needing glasses isn't one of them.