From Bulbapedia, the community-driven Pokémon encyclopedia.
Watt (Japanese: ワット Watt) is the assistant to Wattson. His name comes from "watt", which is the SI measurement of power.
He has appeared in two episodes of the anime. His first appearance was in Watt's with Wattson?. He more or less stood aside and let Wattson do everything, although he did serve as the referee in Ash's Gym battle for the Dynamo Badge.
When Ash and the others returned in Manectric Charge, Watt was featured much more prominently. He battled May and her Skitty with his Ampharos. Skitty proved to be stronger and defeated Watt's Ampharos. Watt was also the one to inform May about the Pokémon Contest in Verdanturf Town.