That the first men to walk on the moon brought pokeballs with them was wholly unremarkable; after all, the pokeball had played a key role in the history of spaceflight. Only by returning to their pokeballs had the Growlithe and Simisear test pilots who preceded humans into space survived the scorching temperatures of re-entry; even their fire typing couldn't protect them from serious injury before they sought the safety of their pokeballs. Experiments to modify pokeballs so they could capture humans and leave them in stasis for lunar or interplanetary journies had failed, but they had provided key insights which led to the development of spacesuits.

That some of these pokeballs contained pokemon was also unsurprising; humans had for millennia brought their pokemon with them everywhere, and space agencies were intrigued by the idea of experimenting on how a wide variety of species reacted to zero gravity, so they had no cause to object.

That some of the pokeballs were empty, however, was nothing more than a fateful oversight. Astronauts were pokemon trainers, and pokemon trainers who did not have a full team of six strapped empty pokeballs to their belt's other slots. On Earth, this was done so they could add any wild pokemon they captured to their team, but that they had done likewise when going to space was simply an absentminded adherence to custom.

The strange-looking ships they passed on their way to the moon were dismissed as the lunar probes of other nations which closely valued their secrecy, their brown or blue pilots mistaken for elaborate machinery. The crescent rocks that earlier unmanned probes had shown dotted the moon's landscape were assumed to be the result of meteor impacts; the tall, pinkish blobs were piles of lunar dust, made up of rare minerals from the moon's core which scientists had spent the last years debating.

It was not until man walked on the moon, going some distance from his spacecraft in search of rare minerals to gather, that he was greeted with the strange and familiar visage of hostile wild pokemon; the sounds of "Clefable" and "Lunatone" were new, but what they meant was all too familiar. It was hard to escape in a space suit, and no one would bring a Repel to the moon; he had no choice but to battle the pair.

His choice of pokemon was made simple by circumstance; the oxygen-poor lunar atmosphere would not allow his three biological pokemon to fight, and it didn't hurt that Magnezone appeared to have a type advantage – the creature chanting Clefable looked like a fairy, and the one grunting Lunatone was clearly a rock.

The battle, however, was not nearly as easy as the astronaut expected, even once making allowances for the fact that he was fighting two-on-one. The moon's magnetic field is far weaker than Earth's, and the magnet pokemon spent much of the match disoriented, struggling to move only as much as it wanted and aim its attacks in the strange lunar environment. The far-better adapted Lunatone manuevered its massive, legless body away from the Mirror Shot with the speed of a Pyroar and send psychic waves crashing into his Magenzone's three heads, while Clefable's tiny, apparently decorative wings let it fly above the moon's surface and shoot powerful, pink, spherical blasts at the moon below.

The fight continued to Magnezone's detriment until it resorted to discharging its electricity throughout the lunar air, blanketing the whole battlefield with electric shocks too wide-ranging to dodge. The astronaut had never intended to throw a pokeball, but he feared the wild pokemon would attack him next, and the nearest pokemon center (provided his spaceship was undamaged and could take off in the presence of hostile pokemon) was hundreds of thousands of miles away.

The sphere connected with the Clefable – the faster of the two, and the more dangerous pursuer now that he had got the hand of lunar movement - and shook thrice as the astronaut waited in fear for his life and that of his badly wounded Magnezone, then sealed shut. He defeated and captured the Lunatone with considerably less concern; once the fight became one on one and his Magnezone began to grasp low gravity it seemed little different from an ordinary pokemon battle, although the species he captured had never been seen before on earth.

When the astronaut returned to his craft, he found it cracked and damaged – by either lunar weathering, an unnoticed botched landing, or yet more lunar pokemon. But before he noticed the cracks, he noticed the little green-blue monsters crawling over it – and these ones were repairing it bit by bit with technology he had never seen on earth, while chattering to each other in a language which to his ears seemed composed of three letters; L, G, M. The apparent leader of the group, a larger, brown specimen with glowing green eyes, spoke a somewhat different dialect, replacing "Bi" for L and "Hee" for G – and minutes after he returned, his spaceship was completely repaired.

When he landed on earth, the astronaut struggled to sleep and train his pokemon amidst all the reports and interviews, as the world struggled to comprehend what he had found. His Clefable would lay a clutch of eggs soon after returning to earth, that its wings did not allow it to fly on his world's gravity, and that the children would evolve from Cleffa to Clefairy (a form later expeditions would find a short-lived transitional phase akin to Metapod on the moon) just fine, but could only become Clefable in the presence of the mysterious lunar stones he had carried with him to earth. Weirder still, three species of pokemon native to earth also learned to evolve with these stones into new forms never seen before by Earthlings, even the few who walked on the moon.

The lunar exchange had begun, and after a few years' expeditions, it would dramatically alter the environments of both worlds – creating strange new ecosystems both orbiting the earth, and in a mountain where new species of pokemon and those introduced by astronauts mixed with Zubat and Geodude, which would soon be renamed "Mount Moon" after the origin of its new inhabitants.

The universe is vast, and what had once called itself the "Pokemon World" had learned it was far from alone.