Although Cat-Man was a fictional comic book character that John Stewart read about in comic books as a child, Catman actually existed in real life in a parallel universe. In the 1950s, He was a member of the legendary team of superheroes known as The Justice Guild Of America. He was often paired up with Black Siren during field missions. He had a Cat-Cycle that he would ride as well. He was also quite athletic and was quite a skilled martial artist as well. He fought crime alongside his teammates until he was killed in a nuclear war.
The Cat-Man encountered by the Justice League was a projection of Ray Thompson's mind.