In the mid-1950s, Batman began to have interdimensional and outer space adventures instead of just fighting street-level thugs and weirdos. So, in Batman #113, our hero makes a strange trip to visit a tattered, multicolored Batman from Planet Zur-En-Arrh who needs Earth's Batman's help fighting an alien invasion. Though given Zur's costume, Batman really should have just arrested him for his crimes against fashion.
If this wasn't strange enough, modern Batman writer Grant Morrison included the formerly forgotten, insane adventure from Batman's zany comics history into being some kind of trip into Bruce Wayne's personal Imagination Land. Apparently, Batman himself created "Zur-En-Arrh" Batman as a "back up personality" in case he ever went insane—because people can be backed up like hard drives, apparently.