Dario Argento's The Phantom of the Opera

Standard story of the Phantom does have one major variation - The phantom is not a disfigured individual, but rather is an unwashed orphan abandoned in the sewers under the Paris Opera & raised by rats. The Phantom invokes death upon anyone who dares harm his beloved rats. In fact, The Phantom's nemesis is the chief exterminator (Istvan Bubik) who develops a rat-catching machine.