Continuity mistake: When Sylvester enters his mother's house, he slides the glass door from the wall to the middle and right to left (from viewer's perspective). But when he closes it, he closes it from right to left so it closes in the middle, even though it wasn't set up that way.
Continuity mistake: When Granny tells Sylvester to stop chasing Tweety Bird, he comes to a stop and Tweety Bird keeps going and is ahead of him. But in the next shot, Tweety is now behind Sylvester (between Sylvester and Granny), however, there's not enough time for him to fly back that far (or even circle around), and we would have seen him do it.