Orphaned when his parents were slain during a expedition in Egypt, Billy Batson was taken in by an ancient wizard. It was there Billy learned that by saying the name of the wizard -- "Shazam!" -- he would be struck by magic lightning and transform from boy to man... becoming the World's Mightiest Mortal -- Captain Marvel! Although he may appear to be an adult when he is Captain Marvel, in fact Billy is still a young boy, with a young boy's naivete about the world. He is an optimist himself, and cruelty in others sometimes surprises him. Recently, Billy was reunited with his long-lost sister, Mary, who also can call on the power of Shazam. Billy and Mary subsequently donated a fraction of their power to their friend, Freddy Freeman, who was crippled when he accidentally stumbled onto a battle between the Marvels and one of their foes. Freddy can summon the power, but unlike Billy or Mary, and due to the source of his power, Freddy speaks the name "Captain Marvel" to be transformed. The group is loosely referred to as "The Marvel Family" when all three are in their super-powered forms.

By speaking the magic word, "Shazam," Captain Marvel is granted the wisdom of Solomon, the strength of Hercules, the stamina of Atlas, the power of Zeus, the courage of Achilles and the speed of Mercury. Likewise, his sister Mary and their friend, Freddy Freeman, can draw on the power of Shazam by speaking their magic words. However, whenever more than just one of them transforms, the power is split between them all, lessening their individual might.