Continuity mistake: When Sylvester is at the medicine cabinet, he takes out a bottle of Seasick Remedy and starts drinking it. But when we see Tweety in the cabinet in the next shot, the Seasick Remedy bottle is still on the shelf when it should be in Sylvester's hand.
Continuity mistake: When Tweety tries to make Sylvester seasick with his picture of a boat, you can see the hull of the boat has three portholes, but when we see a close-up of Tweety in the next shot, there are now four.
Continuity mistake: When Granny and Tweety are resting, Sylvester grabs Granny's glasses and paints a picture of Tweety on the right lens. When Granny puts on her glasses after she hears Tweety calling for help, the picture of Tweety is now on the left.