Agatha

Agatha is a ghost-type using member of the Elite Four in Generation I and its remakes. She was Professor Oak's rival when they were young. She also makes an appearance in the anime where she battles Ash while she is the temporary Gym Leader until someone could be found.

In the Anime
Agatha appeared in the anime series episode 408:Scheme Team. She was seen in Viridian City where Scott invites Ash to Battle Frontier. She battled Ash and won using her Gengar against Ash's Pikachu.

FireRed and LeafGreen
Rematch

Pokémon Stadium
Gym Leader Castle Gym Leader Castle Round 2

In the manga
Agatha

Trivia

 * Apparently, in the Game and Manga, she mentioned Professor Oak, this could mean that she used to have some kind of relationship with Professor Oak.
 * In her Generation I sprite and artwork Agatha had long gray hair.