Audio problem: When Donald O'Connor walks onto the keys of his piano at the beginning of his Make 'Em Laugh Sequence, the sound that we hear is a chord, but in reality we would hear a much more dissonant combination of notes, because several notes adjacent to each other would be played at the same time.
Audio problem: When Bugs says "There's gold in them thar hills" when he comes into the shop carrying a gigantic piece of gold, his mouth doesn't move.
Audio problem: When Elmer Fudd says "Ahem!" when he sees a woman (Bugs Bunny), his mouth doesn't move.