40. Let's Add Some Mini Me, But Don't Make It Too OvertThe only "major" American actor cast in the Potter films was Verne Troyer (of The Spy Who Shagged Me fame), who played Griphook, but even then his voice was dubbed in by Warwick Davis, who took over the role in the Deathly Hallows films. Zoë Wanamaker (Madame Hooch) was born in the U.S., but made her fame as a British actress.
39. Neville's Memory CharmLuke Bailey of Buzzfeed found a delightful one about Neville Longbottom just last week: In the first movie, Neville gets a Rememberall from his gran in the owl post, but comically doesn't remember what he's forgotten. But if you look at his fellow Gryffindors around the table, it becomes obvious; he's the only one not wearing his Hogwarts robes.
38. To Open, Tap And Say DissendumThe humpbacked witch statue seen in the third floor corridor in The Philosopher's Stone is the secret entrance to Honeydukes portrayed in the novel Prisoner of Azkaban. Of course, none of our trio knew this, as Fred and George wouldn't be giving Harry the Marauder's Map until Year Three.
37. Switching SidesAt the beginning of the Quidditch match in the first movie, Madame Hooch is wearing the Hogwarts emblem on her left chest. When she announces that Gryffindor has won, its moved to her right. But it's not a case of simple image reversal - the positions for the logos for the houses match in both scenes. And what's with those eyes? Did she attempt to become an Animagus like Professor McGonagall and just kept the eyes? Or did she take a cross-species drink of Polyjuice Potion?