Billy Batson, according to DC Comics lore, is the young boy who is granted the power to turn into a hulking superhero just by shouting the word "Shazam!" Billy receives this power from a wizard, and is able to wield the power of lightning as a result of his gift. It also explains why Shazam carries a child-like exuberance when crime fighting, and we always assumed that Zachary Levi's Shazam would be a stand in for a child actor cast as Billy. Now we can confirm that DC is going to take that route with their origin-story movie.