Continuity mistake: When Sylvester is looking at Tweety in his cage in the pet shop window at the beginning of the cartoon, you can see Sylvester is resting his arms on the window sill. In the next shot, he now has his left hand under his chin.
Continuity mistake: When Sylvester takes out the packaging in the box, he puts himself in the box and you can see it is lying flat on the ground. But when Granny opens the gate to collect the box, it is now resting against the wall.
Continuity mistake: When Granny collects Tweety Pie from the delivery man, the handle on the gate is on the left hand side, but when the postman comes to put the parcel in the mail box, the handle is now on the right.
Continuity mistake: When a postman comes along with a parcel for Granny, he puts it in a postbox by the front gate of Granny's home. The postbox was not there previously when Granny collected Tweety Pie from the delivery man earlier in the cartoon.
Continuity mistake: When Sylvester is looking at Tweety Pie in the pet shop window, you can see the cage next to Tweety's cage is much further away, but a couple of seconds later it is now next to Tweety.