Wattson resides in Mauville City and is an expert on Electric-type Pokémon; defeating Wattson will earn the trainer the Dynamo Badge. His English name is derived from watt, while his Japanese name is likely a reference toward Nikola Tesla. An old man, Wattson is almost always seen smiling.

Inside his gym includes several electrical doors and trainers. Each door can be opened by stepping on a switch. His puzzle isn't very difficult, much less than the next Gym Leader, Flannery. After his defeat, he hands you TM34: Shockwave, an electric attack that is sure to hit.

As shown in the Pokémon anime, Wattson always likes a good joke, as any visitors (gym challengers or not) take a roller coaster ride, ending up against a mechanical Raikou. Ash surprisingly defeats Wattson easily with just his Pikachu, which is unusual as Electric-type moves are not very effective against Electric-type Pokémon. Wattson then dejectedly plans to retire from his Gym Leader post but regains his fighting spirit after helping to defeat Team Rocket. It is revealed that Pikachu's electric attacks had been temporarily supercharged when he destroyed the mechanical Raikou, which allowed him to overwhelm Wattson's Pokémon. Ash, hoping to get a fair rematch, tries to return his Dynamo Badge and earn it back fairly, but Wattson asks him to keep it because Wattson realizes that he also needs to continue training. His training pays off, because he and Ash meet again later in the series and have a rematch, in which Wattson's Manectric defeats Ash's Torkaoal.