Batman Day is more than just an excuse to dust off comics or binge movies. It is a reminder that the Dark Knight is cinema's most enduring shapeshifter. Unlike many superheroes who remain tied to a fixed image, Batman changes with us. One decade he is a wartime patriot in a trench coat, the next he is a camp crusader dancing to surf-rock, and in another, he is a solitary detective scribbling his failures into a leather-bound journal.Every Batman is less about a definitive performance and more about the mood of the world around him.