Previously we had considered the two Martian Manhunters and the two Robotmen of Earths One and Two. J'onn J'onzz and Roh Kar were indeed the preeminent protectors of the fourth planet from the sun who came to their respective Earths to defeat fellow Martians who invaded their neighboring worlds. And Cliff Steel along with Robert Crane were adept adventurers who made the most of living their lives within robotic bodies after their human frames had perished due to tragedy. So why would we say that the careers of J'onn and Robert were parallel when each had his own unique counterpart of the other's world? As we shall see, it is due to mitigating circumstances that cause divergences on each Earth wherein key events caused ripple effects that effected other people, places and things in each reality. Such as our two featured players today.
While Cliff Steele had dozens of adventures alongside the Doom Patrol as one of its members, the same could be said for Robert Crane. And yet, Crane's alter ego Robotman had over one hundred and forty solo cases of his own during a span of some thirteen years before he mysteriously left Earth-Two. Similarly, while J'onn J'onzz had his own thirteen year career on Earth-One as the Martian Manhunter which covered over one hundred and forty solo tales before he too left his adopted home world, although his twin Roh Kar left Earth-Two after a single case alongside Batman and Robin. What gives? Well, for a sizable period of the past decade, Cliff Steel laid it in coma at sea following the end of his Patrol when he and his team were all left for dead by two of their enemies. As for Roh Kar, after defeating fellow Martian known as the Stranger, his mission was completed and he returned to his former career on Mars-Two. However, J'onn could not return to Mars-One as he had already been living in exile for years due to a conflict between his Green Martians and the rival White Martians, a conflict that never took place on Mars-Two. Cliff would eventually be revived, and undoubtedly Roh's career would have continued, but that is not who we are principally considered this day.
Meanwhile, J'onzz as first police detective John Jones and then later as the Martian Manhunter decided to assimilate into humanity and provide it protection with his bountiful supply of superpowers. Similarly, Crane under the assumed identity of crime investigator Paul Dennis and then Robotman likewise decided to use his new abilities to aid his fellow man even though he was no longer physically one of them. The Jones and Dennis aliases were simply a means for these two non-human heroes to feel like they were a part of Earth society rather than being the outcasts that their true appearances revealed. Still, each incurred enduring relationships with others, such as Jones partnership with police woman Diane Meade and Dennis' courtship with socialite Joan Carter. Neither of these couplings lasted as the two inhuman invaders realized that such a bonding would not work on various levels. In fact, for a time the pair's closest allies was J'onn's shape-changing friend Zook and Paul's robotic dog Robbie. Nevertheless, they proved among the most human of heroes in the depths of compassion and courage with which they showed.
Each possessed superstrength, the power of flight and extendable bodies, the ability to mask their appearance and greater perception than the normal man... among other attributes. And both manhunters had keen intellect that allowed them to create a variety of scientific marvels as well. While the Martian Manhunter of Earth-One eventually left to find and lead his fellow Martians in their new world after their own had been devastated, the Robotman of Earth-Two was convinced to journey to Earth-One to restart his career at which point soon after he was left in a coma in a mindshaft for two decades. Eventually, J'onn would return to Earth-One to rejoin his old team, the Justice League of America. And Paul would also return to Earth-Two and with his brain now implanted in his late colleague Chuck Grayson's preserved body aided the Justice Society of America in their time of need.