Ash has a new Pokemon companion.
After months of speculation, Ash officially caught the Ultra Beast Poipole in today's episode of Pokemon the Series: Sun and Moon. Poipole is an extradimensional Pokemon that came from the mysterious Ultra Space, a dimension that can only be accessed via Ultra Wormholes.
Poipole first appeared several months ago, when it was shown sneaking into the Alola region via an Ultra Wormhole shortly after Ash and his friends made their own excursion into Ultra Space. Poipole seems to be attracted to electricity and eventually found Ash and Pikachu after sensing Pikachu's electricity. While Lusamine (an expert on Ultra Beasts and Ultra Space) recommended that Poipole be returned to Ultra Space, Ash and his friend's can't do that until they find an Ultra Wormhole. So, Ash captured Poipole to keep it around, especially as it got along so well with his team.
As you can see in some of the screenshots below, Poipole is an incredibly cute and affectionate Pokemon and should fit in nicely with the rest of Ash's Alola team:
Poipole is a new Ultra Beast, having first made its appearance in the Pokemon Ultra Sun and Ultra Moon video games. Poipole is the only Ultra Beast that is known to evolve, as it eventually turns into the powerful and dangerous Naganadel.
Ultra Beasts aren't technically Legendary Pokemon (at least, not according to Pokemon's official Legendary website), but they do share many of the same characteristics. Ultra Beasts are genderless, can't be found in the wild, and have incredibly powerful stats. They're also incredibly hard to capture in normal PokeBalls (although Poipole does come in a PokeBall in the video games as it's given to the player instead of captured.)
Poipole adds another potentially powerful Pokemon to Ash's team, which currently consists of Pikachu, Rowlet, Torracat, and Lycanroc. Ash also has a Rotom that isn't considered a part of his team as he never caught it and it's unable to battle. Ash also unofficially had a Solgaleo (a Legendary Pokemon from Pokemon Ultra Sun) on his team, but it left the group after helping Ash rescue Lusamine in Ultra Space. Like Rotom, Ash never technically caught Solgaleo.
We'll see how long Ash has this powerful Pokemon and whether it will come in handy dealing with future Ultra Beast encounters. Just don't get too attached to Poipole, as Ash will likely have to let it go before he departs the Alola region to go on his next adventure.