Captain Marvel Jr. is the alter-ego of Freddy Freeman, who gains the Powers of Shazam when he says the words “Captain Marvel”. He can change back to Freddy by repeating the same words, “Captain Marvel”. (This is often inconvenient, as when he is in his heroic form, he can't even introduce himself!)

Freddy walks with a crutch as his left leg is paralyzed and almost useless, the result of brutal injuries he sustained in a confrontation with Captain Nazi during World War II. In that same confrontation, the villain killed Freddy's grandfather. After Freddy recovered from his injuries enough to walk using a crutch, he supported himself with a newsstand, on the corner of Oak and Main in the neighborhood of Fawcett City in New York City, and he lived in Mrs. Wagner's boarding house. In the present (late 80s) on Earth S, Freddy still operates a newsstand on the same corner, now rents the entire basement of Mrs. Wagner's house, and is a student at Columbia University.