Oswald is a minor character who showed up in the Pokémon anime episodes "Clefairy Tales" and "The Electric Tale of Pikachu." He's basically obsessed with space and aliens, living in a small Kanto town where he's surrounded by tech he bought through comic books—none of it actually works.
When Clefairy start mysteriously stealing stuff from the townspeople, everyone's confused. Oswald, though, is convinced they're extraterrestrials gathering materials to build a spaceship. Nobody takes him seriously except Ash and his crew, who decide to help him track down the Fairy Pokémon. They even team up with Jigglypuff along the way.
Sure enough, the Clefairy are legit assembling a spacecraft using all the stolen goods. Once the ship gets ready to launch, Ash and friends bail out—but Oswald stays behind because he's desperate to stick around and learn more about what he's certain are actual aliens. His commitment to the bit is honestly kind of endearing.
The Clefairy and their UFO do make a comeback in "Wish Upon a Star Shape," but Oswald only appears in a flashback. He doesn't actually show up in person for that one.
Content compiled by AnimeList.moe from publicly available sources.
