Continuity mistake: When Homer is sitting in the Frying Dutchman with the crowd gathered round looking at him, the Captain invites people in. Some start walking in, but in the next shot where they are all gathered round again, it is the same group of people again.
Continuity mistake: You may have to look carefully for this mistake. When Marge picks up the 'Das Butt' video, you can see the cover. In the next shot, you can see Marge holding it so you can't see the cover. But when she hands it over to Ruth, she twists the video round and you can see that nothing is visible. You may have to see it a couple of times.