>>53287706Back in the original games, when the setting took place in more or less the real world and Pokemon were implied to be these scary unknown entities that had only recently appeared (hence why people knew so little about them), Mt. Moon was one of the many, many hints littered throughout the game that Pokemon actually originated from outer space. The Clefairy worship a meteor that crashed there (stated in RGBY but not actually visible until GSC), with the Moon Stone items supposedly being fragments of it (and implying that all the other evolution stones are also meteor fragments). The presence of Pokemon fossils here also implies this isn't the first time Pokemon hitched a ride on a meteor to get here - it was happening in prehistoric times as well, though not in as great a number as the present.
Of course, with all the later retcons from Gen4 onwards, the place has lost it's meaning - now, Pokemon have always been here, real animals don't exist, and Pokemon Professors are actually just really stupid because, despite the previous point of 'Pokemon have always been here and are this world's equivalent of real animal's, they apparently still don't know jack about them after all this time.