Continuity mistake: When Porky thanks Sylvester for saving him, Porky is wearing a nightcap on his head. When the mouse in the cuckoo clock knocks Sylvester unconscious with a mallet, we cut to Porky and the nightcap has disappeared.
Plot hole: When Porky walks up the stairs to his bedroom, Sylvester is clinging on to his back, still terrified. When Porky is in his room, he has somehow removed his clothes with Sylvester still clinging on to his back.
Continuity mistake: When Porky sends Sylvester down the stairs to stay in the kitchen, Sylvester crashes into an umbrella stand and there are several umbrellas in the stand. But when we see Porky at the bottom of the stairs a little later on, the stand is now completely empty.