The Wonder Trade feature in Pokemon Sun and Moon is dice roll: You put a Pokemon in, get a random Pokemon from somewhere else in the world in return. Out of 700+ possibilities, players keep spotting Yungooses named Donald Trump circulating on Wonder Trade.
Fans have thought the reality TV star and the Alolan Pokemon have looked similar since the Pokemon was announced. He does kind of look like a rodent with a bad combover, doesn't he? Youngoos is also an extremely common Pokemon in the early stages of the game, which makes it easy to grab an extra one for a quick gag.
One might assume that naming this monster after the United States President-Elect is some kind of political statement. Perhaps they're mocking the guy by comparing him to a cartoon weasel. Perhaps they're one of those particularly edgy individuals that thinks sending the words "Donald Trump" into the ether will have a negative emotional affect on a stranger. For what it's worth, I caught a Yungoos with the intention of Wonder Trading him. I nicknamed him HaveANiceDay. Here's to hoping you'll see him soon.