In Pokemon Red/Green/Blue, an older man is tamping land in Vermillion with his Machop. He says he's preparing for construction.
In Pokemon Gold/Silver, the same man, even older, says he's still preparing the construction, now with a Machoke. However, he doesn't have enough money.
In Pokopia, in the ruins of Vermillion, a tablet reads that a man named Kenzo, owner of the largest building in the area, completed construction with the help of a Machamp. Presumably the old man traded his partner to his son, causing it to evolve.
In Pokopia's kind of bleak world, it's real nice to see these happy little easter eggs. I was so excited when I understood the reference!
by darthmeteos