Continuity mistake: When Sylvester is angry that the blade of the axe flies through the mail slot, he strikes the can of tuna with the grip and in doing so crushes the can. When we see Sylvester setting up a piano a little later on, the can is undamaged.
Continuity mistake: When Sylvester opens the final cupboard door and finds tins of food in it, you can see that he is holding on to the door at the end of the shot, but as the shot changes he now has his arm by his side.
Continuity mistake: When Sylvester tries to open the front door, you can see there is nothing under the handle, but when Sylvester opens the letterbox in the next shot, a key hole has suddenly appeared.
Continuity mistake: When Sylvester discovers that the cupboard door has a lock on it at the end of the cartoon, he is holding a can opener in his right hand, but after we see a close-up of the lock, we return to Sylvester and the can opener has disappeared.