[Yes, I know it’s January] asks:

Is there a Pokémon version of Christmas? Is there, like, Arceus-mas or Arce-easter where people celebrate Arceus instead of Jesus? I’m pretty sure there was a winter festival about gifts or something in the anime.

Well, the Kanto series of the anime had a literal Christmas episode – like, they met Santa Claus and everything.  So the easy answer is yes, Christmas exists, takes place during the northern hemisphere’s winter and is associated with gift-giving.  Therefore, Jesus, St. Nicholas of Myra and the Christian faith all exist, therefore the Roman Empire existed and the date of Christmas was fixed at December 25^th at some point during the reign of Constantine I in the 4^th century (probably by the logic of that date being nine months after Passover, which was thought to be the date of Jesus’ conception, which in turn means that both Egypt and the Jewish people exist); in addition, if the birth of Jesus was a significant event we have to assume that his death was likewise significant and that Easter therefore also exists… and so on.

I said that was the “easy” answer, didn’t I…?

The better answer is that, in modern Japan, Christmas exists and is popular, but is largely divorced from any religious meaning and is mostly a celebration of Western exotica (which I talk about a little bit here; there’s some fun trivia if you don’t know anything about modern Japanese Christmas).  The creators of Pokémon mostly don’t care about the origins of Christmas, so the writers of the anime can just copy-and-paste the modern, stylised and hyper-commercialised version of the festival into their world without importing any of its history.  Maybe the Pokémon world has a totally different alternate history that just… somehow happens to converge to a holiday called Christmas that is recognisable as such to a modern Anglophone audience.  I don’t think there is an equivalent, like, “Arceus died on the cross for your sins” (or whatever) narrative going on, because I suspect that religion in the Pokémon world – as in modern Japan – exists more in diverse, localised traditions and rituals than in organised worship and centrally-mandated dogma.  Arceus is important in Sinnoh (or at least, was important in ancient times; it seems like ordinary people don’t really know anything about Arceus anymore), but might not such a big deal everywhere else, where people may have had totally different beliefs about the origins of the world.  In the absence of more specific evidence for the widespread worship of any particular deity, I’m not sure I believe there are major “world religions” like Christianity or Islam in the Pokémon world at all.

…also I think it’s worth repeating that the kids literally meet Santa.  He is real and they meet him.  Maybe he just fµ¢£in’ made Christmas up and everyone else in the world said “well, at least he comes down our chimneys with gift-wrapped presents and not a pile of knives; all hail the jolly fat man.”