Harry Potter and the Prisoner of Azkaban - Marauder's Map Mess Up!
During the credits, right about 2:15 minutes into the movie, if you read the names of some of the rooms on the map in the background, you see that one of the places is called "The Stinkbomb Shop" or something like that. Then about a minute or so later you will see a shop called "The Book of Monsters Repair Shop", both of which are in Hogsmead. The stinkbomb shop is part of Zonko's Joke Shop, and the other shop is part a another shop... But , it is clearly explained both in the movie and in the book that the Marauder's Map sees only inside of Hogwarts grounds, therefore the map could not contain either of these shops, considering that they are in Hogsmead... A small mistake that led to a long explaination by Yours Truly... Have fun looking for more Slip Up's!
Full screen special edition version.