The "Harry Potter" franchise of books and films has a frighteningly loyal fanbase. Even over 10 years after the final film of the series was released, fans still talk about and base their entire personalities around "Harry Potter." For them, the actors who brought their favorite story to the big screen are legends. But not all of those legends enjoyed being part of the franchise.

Alan Rickman did not count himself among the legions of "Potterheads," according to his recently revealed diary entries. Rickman, who portrayed the cold and mysterious Severus Snape in all eight of the "Harry Potter" movies, has never been afraid to criticize films in the past. An actor of his caliber is often given some leeway in being a bit rude about projects they see as beneath them. But to see how poorly he felt filming "Harry Potter," and how often he considered leaving, is a bit...