Superman has been around for a very long time, and has had many things happen to him. On of which was the Superman Red/Superman Blue storyline that occurred in 1963, and then adapted again in 1998.
In the Superman Red/Superman Blue one-shot (February 1998), a trap created by the Cyborg-Superman caused Superman to split into two beings who represented different aspects of his personality, though each believed himself to be the original. Superman Blue was the more cerebral entity, preferring to think his way out of situations and actually solve problems with his mind as well as his powers. Superman Red was more trash, but also more decisive, preferring action over taking the time to think. Over time these two personalities grew more and more polarized and individual, to the point that neither entity wanted to become one Superman again.
This begs the question