When he was a Sergeant, Mayhem was a member of Z-COM. His unit developed a time machine to stop an invasion by Gray aliens before it began. Before it could be used, the machine was captured by Hannibal, Face, B.A., and Murdock. They jammed a rake into one of its holes, causing them to be blasted into Timeless Space.
Upon becoming a General, Mayhem shows interest in the military applications of zombies, believing that they would make perfect soldiers -- unable to think for themselves, and unable to die because they are already dead. He pays Bun-bun a hundred thousand dollar advance to create zombies, but Bun-bun simply hires some college kids to dress up as zombies. Mayhem is subsequently arrested by the military police for stealing millions from the military to fund scientists trying to raise the dead.