10 Insane Rules Movies Weren't Allowed To Break
2. All Main Cast Members Had To Be British - Harry Potter
It's not at all surprising that Harry Potter author J.K. Rowling exerted an enormous amount of creative control over Warner Bros.' movie series, yet one of her more unexpected stipulations pertained to the nationality of the main cast.
Rowling insisted that the ensemble be made up of British actors and was firmly opposed to any Americans being cast, in an attempt to preserve the distinct "Britishness" of her stories.
This led to Robin Williams being turned down for the roles of both Hagrid and Professor Lupin, and as casting director Janet Hirshenson quite aptly put it, "Once [original director Chris Columbus] said no to Robin, he wasn't going to say yes to anybody else, that's for sure."
The rule was strict enough that even though American director Columbus' young daughter Eleanor was allowed to play the small role of Hogwarts student Susan Bones, she wasn't allowed to speak in the movie due to being American.
In the filmmaker's words, "She worked about 80 days... but she never spoke because you know the rule was if you're not British, you can't speak."
Though there are a few other fudgings of the rule throughout the series - such as Irish actors Richard Harris and Fiona Shaw, and American Verne Troyer in a non-speaking role - for the most part Rowling held firm over the course of the eight Potter movies.