Episode #124 - The Chikorita Rescue
Ash saw a Chikorita, and tried to capture it. He tried a few of his Pokemon, but were beaten by Chikorita. Even the mighty Charizard was beaten! This was a very high level Chikortia. But Chikorita was hurt, and was rushed to the pokemon center. There, Team Rocket pretended to be doctors, and took Chikorita. Then they got on a car and got away, thinking Ash won't be able to get them this time. Ash soon caught them, but accidentaly left his pokeballs back at the center. So Chikorita and Pikachu gave Team Rocket a whipping, and became Ash's Pokemon.