Continuity mistake: When Elmer opens the door to the hungry cats, you can see that there is only a handle on the door, but when one of the cats demands more money, Elmer slams the door and the handle now has a lock with it.
Continuity mistake: Park Ranger Donald is leading five bears to a cave, so they can hibernate for the winter. He finds a bear sleeping in a hammock and forces him to join the others. There should now be six bears but a seventh bear has appeared out of nowhere. Later in the cave, their number has grown to nine.
Continuity mistake: When Calvin Q. Calculus has invented the portable hole, he says "Eureka!" and you can that there is a beaker on the desk, but in the next shot the beaker has disappeared.
Continuity mistake: When the coyote is about to eat a tin can at the start of the cartoon, the bottle of wine in front of him changes position between shots.