On its surface, Pikmin is a cute strategy game about growing little plant people and gathering treasure. Delve deeper into its lore, however, and you'll find fans debating the series' apparent commentary on human extinction, and all sorts of timey-wimey shenanigans going on to make its many story elements match up.
Spoiler warning: the following article discusses endgame details for Pikmin 4.
Before Pikmin 4, I'd never spent much time trying to make Pikmin's setting make sense. It's based on Earth, obviously, though a version with different animals and no humans in sight. And yet, you can still run around and find evidence of human existence - and seemingly very recent human existence at that, with freshly-baked food and other objects simply lying about. Are humans extinct, or have we all simply popped out for tea? It doesn't really matter to the simple stories Pikmin games tell.