Atsuo

Alan is a character of the day who first appeared in Nosing 'Round the Mountain!.

He met with Ash and his friends while they were passing through Mount Coronet. His dream was to evolve his Nosepass, so he challenged Ash to a battle in order to level up his Nosepass knowing that the special magnetic field present in the area would trigger the evolution. After the battle, Nosepass did evolve, but then, Team Rocket used a mind-controlling helmet of their creation dubbed the "Probopass Power Mind Manipulator" to control Alan's Probopass. Team Rocket's plan ended up failing and Alan got back his Probopass.

He reappeared in a flashback in Playing The Leveling Field!. It was revealed that Alan was one of the Trainers who faced Fantina in battle and, after losing, managed to beat her in a rematch.

(Source: Bulbapedia)