Marvel Man, also known by his secret identity as the prisoner Ken Clark, was a superhero on the planet Terra, who bore many resemblances to Superman on the distant planet Earth. Instead of Kryptonite, his weakness was Diamond. His relationship with Marvel Maid was the opposite of Superman's relationship with Supergirl: Marvel Man was the second to arrive on Terra, and Marvel Maid kept him as her secret weapon, during which time he had to remain in his secret identity at the prison. When Supergirl visited Terra, she became friends with Marvel man and stayed to see him finally revealed to the world. ("The Second Supergirl!")