Revealing mistake: When Tom is punctured in the rear by the fork that Nibbles is holding, his tail is missing.
Continuity mistake: When Jerry hears the door bell, he puts the magazine he is reading on his chair. But when Nibbles attempts to take the cheese off the mousetrap, the magazine has disappeared.
Continuity mistake: When Nibbles launches a candle into Tom's tail, it burns him and turns Tom's fur brown. When we see Tom waving his white flag in surrender after he has crashed into the cabinet, his fur is now blue again.