Erika is the Gym Leader of the Celadon City Gym. Her first appearances were in Pokémon Red, Pokémon Blue, Pokémon Yellow and Pokémon Green. Her first anime appearance was in the episode Pokémon Scent-sation, where she told Ash that he could not challenge her gym as it was female-only.
Erika is the stereotypical girly-girl in the sense that she only collects Pokémon that she believes can be attractive (this seems to be mainly taking the appearance of a flower). However, she is mature enough to teach classes of "flower arranging". She appears to be quiet, but is well known in her hometown of Celadon City.
She always seems to be tired, though this could just be her light-headedness from the aromas that her grass Pokémon let off. She nods off very often, though the only thing that is needed to fire her up is an interesting Pokémon battle.
When defeated, Erika gives out the Rainbow Badge in all of the video games. In the main games, she gives out TM21 Mega Drain and TM19 Giga Drain. She also gives away a Castle Key in Pokémon Stadium that unlocks Koga's Castle.
In the Pokémon Heart Gold and Soul Silver remakes, she can be found near the fountain in Celadon City from 3-5PM on Saturdays and Sundays when the player is ready for their rematch with her. By calling her on Sunday morning, she will move her location to the Fighting Dojo so that the player can battle her and her improved team.