Xavier Simon was a former member of the United States Army in his youth, during World War I. He was friends with Thomas Wayne and three other members of their group during the war. When Simon committed a crime, his friends gave him up and he was sent to prison for years. When he was finally released, he decided to get revenge on them and he asked a scientist to develop a machine to transfer his body into that of any other being. Upon learning about the death of Thomas, he turned his attention to his only son, Bruce Wayne and spied on him for years, eventually learning the truth of his secret identity as Batman.
His machine was only completed much later when Xavier was already an elder man and after killing the scientist who built it, he used it to transfer his mind into the body of an albino gorilla. Like this, he brutally murdered his former friends and lured Batman into a trap to switch his mind into the Batman's younger body.
- This version of Xavier Simon (Earth-One), including all history and corresponding appearances, was erased from existence following the collapse of the original Multiverse in the 1985–86 Crisis on Infinite Earths limited series. Even though versions of the character may have since appeared, this information does not apply to those versions.
- Although not referred to as such in the story, he is somewhat similar to the Ultra-Humanite in transferring his mind into an albino ape.
- 2 Appearances of Xavier Simon (Earth-One)
- 2 Images featuring Xavier Simon (Earth-One)
- Quotations by or about Xavier Simon (Earth-One)
- Character Gallery: Xavier Simon (Earth-One)