Which movies are based on books?
What books/films do you mean ? Many films are based on books, but many don't actually keep to the facts. I haven't seen avatar if that's what fim you mean but i know twilight doesn't keep to many facts.
There are books about Pirates of the Caribbean, but they have nothing to do with the movies. Rob Kidd wrote books about Jack in his childhood based off of the movies. The movies are based off pf the original Pirates ride at Disneyworld, but the 4th installment is also based off a book called On Stranger Tides. Though i am not sure who the author is, sorry about that.
The question shouldn't be why is she blond in the book, it should be why has she got brown hair in the movies. The books were written years before the movies came out. The movies are based off the books. Therefore anything in the books is canon. J.K Rowling decided she wanted Petunia to have blond hair in her books. However Fiona Shaw, who plays Petunia in the movies, has brown hair which is why…