Deliberate "mistake": I know this has been disregarded for the fun effect, but gasoline motors require air to work. When Edgar drives his tricycle into the river while being chased by Napoleon and Lafayette, it should have stalled and stopped working.

Continuity: When the butler gets placed into the trunk to Timbuktu, from the time he leaves the barn to the moment he gets lifted on the mail truck, a lock magically appears on the trunk.

Continuity: When the cats are running away from the milkman, you will see O'Malley pick up Marie as he is running. However, in the next shot, as they enter the shed, Marie is running in front of O'Malley.

Continuity: Marie falls off the viaduct into the river but doesn't get washed along by the current at all (until they spot her and start the rescue that is).

Continuity: If you freeze the frame when Edger unfurls the newspaper to show Frou-Frou, you will note that the text on the entire front page is a replication of the first paragraph over and over again.