Erika is the Gym Leader of Celadon Gym located in the heart of Celadon City. Trainers that defeat her in a gym battle are awarded the Rainbow Badge as proof of defeating her. She specializes in Grass-type Pokémon as well as selling and making perfumes.
As well as running her gym, she also runs a perfume store nearby where she is the manager.
Erika believes that perfume has the effects of relaxing people's moods, invigorating them and healing their hearts. When
Ash Ketchum entered her perfume store and mocked it as just a means of making guys fawn over girls, he was kicked out of the store and then later out of the Celadon Gym as well. She instructed her subordinates to not allow him to enter the gym because of his perfume remarks.
Essence of Gloom
Team Rocket heard about a legendary perfume that is made in the Celadon Gym and attempted to steal it. They tricked
Ash Ketchum into working with them so they could enter the gym undetected. They ended up destroying the Celadon Gym in a large fire before they stole what they thought was the formula but instead it was Gloom extract which is used as raw material for perfume.
Gym Battle with Ash
Since
Ash Ketchum was banned from the gym, he couldn't challenge
Erika to a battle. He snuck in disguised as a girl and called himself 'Ashley' (Sato-chan).
Ash's Pikachu realized it was him and since he was discovered he challenged
Erika to a battle on the spot which she accepted. She setup the battle as a 3-on-3 but the battle was never fully completed. Her Tangela was sent out first and it managed to defeat
Ash's Bulbasaur with a
Stun Spore, which paralyzed it. Realizing that his Grass on Grass battle technique wasn't working against
Erika,
Ash Ketchum sent out his Charmander.
Erika then told
Ash Ketchum she'd give him a Paralyze Heal after the battle which showed her loving and compassionate side.
Erika's Weepinbell was sent out second to counter
Ash's Charmander but its
Flamethrower proved to be too much for it.
In the final matchup,
Erika's Gloom was sent out to battle
Ash's Charmander and
Ash's Charmander couldn't stand the horrid smell of
Erika's Gloom and was recalled.
Ash's Pikachu was going to be matched up with it for the final round of the battle but Team Rocket exploded a bomb in the gym and it caught fire. Everyone except
Erika's Gloom escaped safely, so
Ash Ketchum decided to go in after it as he thought he was partially responsible for the disaster. As thanks for rescuing her Gloom,
Erika gave
Ash Ketchum the Rainbow Badge.