12 Biggest Retcons In Harry Potter Movies

10. The Gryffindor Common Room Moves

In the first film the Gryffindor common room is situation at the end of a hallway, and the Fat Lady portrait guarding the entrance is played by Elizabeth Spriggs.

But then in The Prisoner Of Azkaban, the entrance changes position to the Seventh Floor of the Grand Staircase Tower. It's the same common room, but Cuaron obviously wanted to take advantage of the other portraits for the scene in which the Fat Lady (now played by Dawn French) flees Sirius Black so he moved it.

On top of that, the portrait swings backwards rather than forwards because who cares about paying attention to detail.