Continuity mistake: After Pongo spots Anita and Perdita walking towards the park, Pongo moves the time forward on the clock and he leaves the dial's hinged bezel open as he rushes to the door and barks, but when Roger checks the time on the clock the bezel is closed. (00:06:20)
Continuity mistake: In the cabin when they are coming up with the idea to swap places, Susan has on white sneakers in the beginning of the scene when she is on the bed, and Sharon has on the black Mary Janes. Later in the scene, with no time to change shoes, Susan is seen walking around the cabin wearing the black Mary Janes.
Continuity mistake: When the two men are carrying water up to their new cave home (via a home made elevator), one of the men is holding two buckets of water. In the shot where you can see the sea behind them, this man hands the second man a bucket of water, which he takes. In the very next shot, from inside the cave, the first man has both buckets and again hands the other man the bucket of water. (00:48:35)
Continuity mistake: The police that come to the aid of the professor are driving an older Ford when they approach than when they arrive to help. The car is a newer model in the later scene.
Continuity mistake: When Sylvester is pursuing Speedy on his motor bike, Speedy stops at the end of the cliff. But when Sylvester sees the cliff, there is now no sign of Speedy.
Continuity mistake: When Sylvester and the bulldog try to blow up the chain with some TNT, you can see the explosive has the wording "TNT" on it. But when the two take the explosive and put it into a hole, the "TNT" has gone. The wording reappears when the explosive falls out of the pipe.
Continuity mistake: When we see the boomerang box, there are words on the side reading "One Boomerang" and "Returns to Owner." When we see the Coyote holding the boomerang in the next shot, both the words on the box have disappeared.
Continuity mistake: When Sylvester is trying to sleep in his bed at night, you can see next to him there is a dressing table and on it there is an alarm clock and a hairbrush. Watch the hairbrush: in some shots it is next to the clock; others it isn't.