Continuity mistake: When Porky realises he's been tricked at the Toll Bridge, he throws his gun in the snow, and when he runs off, you can see there is nothing in his hands. But when Porky arrives back at the Toll Bridge, he is holding his gun again.
Continuity mistake: When Spike is captured by the dog catcher at the end of the cartoon, you can see that there is a padlock on the door of the van, but when Jerry is chasing the van in the next shot, the padlock has disappeared.
Continuity mistake: When Granny is speaking to Sylvester at the start of the cartoon, you can see there is nothing is under Sylvester. In the next shot, a green pillow appears, and in the shot after that, it has disappeared.