Bayleef made her first appearance in "The Chikorita Rescue" when she was a wild Chikorita who Ash and his friends came across while walking through the mountains. Despite her small size, she proved to Ash that she was very tough by defeating his Bulbasaur with a single Vine Whip.
She was stubborn, unwilling to give up and even went against very high odds to fight against Ash's Charizard despite the obvious type advantage. This in turn left her injured and although she wanted to continue fighting, she eventually fainted, forcing Ash and his friends to bring her to a Pokémon Center for treatment. Later on, Team Rocket kidnapped Chikorita and attempted to get her to join their side. However, Ash and Pikachu stopped them and were able to rescue Chikorita, resulting in the tiny Grass Pokémon developing respect for Ash. When Ash left the Pokémon Center, a heartbroken Chikorita, unwilling to be left behind with Nurse Joy ran up after him and begged him to take her with him. In mere seconds, Ash accepted and Chikorita officially joined his party much to her joy.
Chikorita later developed a crush on Ash and began constantly seeking his approval. Whenever she was released from her Poké Ball to engage in battle or stop Team Rocket, she always insisted on hugging Ash much to his discomfort.
It was later revealed in "Chikorita's Big Upset" that Chikorita was female and that she was jealous of Ash giving so much time to Pikachu which had in turn caused her to suffer from envy but she soon got over her worries and developed a friendship with Pikachu.
In the episode, "Current Events", Chikorita, distraught at seeing Ash taking several beatings from Team Rocket's Pokémon evolved into Bayleef to protect him. Not realizing her form had changed since she'd evolved, she kept attempting to jump into Ash's arms as if she was still small.
This caused her to accidentally knock Ash over on several occasions and Ash eventually snapped in "Turning Over a New Bayleef", angrily telling Bayleef to get away and stay away from him. His harsh words left Bayleef in tears and she ran away from Ash, her feelings hurt.
When Ash, Misty and Brock found her after spending many hours searching for her, she'd been taken in by a kind old woman but Bayleef's tears had turned to anger and she refused to accept Ash's apology and stayed put for the time being, refusing to give Ash any attention. Ash, guilty over his treatment decided to stay put in hopes of getting Bayleef to forgive him but she refused his offers, ignoring her and even refusing him. On such occasion, she even hit Ash with her leaf.
Team Rocket later showed up and captured Pikachu and Bayleaf before escaping. Ash then attempted to rescue the Pokémon from a glass cage yet Bayleef refused to help, still believing that her trainer didn't care for her. But after seeing Ash's efforts, she realized that Ash did care after all and her strength was enough to shatter the glass, setting the trapped Pokémon including herself and Pikachu free. After sending Team Rocket flying, she and Ash repaired their broken relationship with Bayleef learning Body Slam in the process.
Since evolving from Chikorita, Bayleef has still kept her longing feelings and crush for Ash which did end up getting her in trouble on several occasions. However after getting used to her size, she managed to become a vital part of Ash's team and helped win many Gym and League battles.
Ash left her at Professor Oak's Lab when he decided to make a fresh start when he left for Hoenn. In An Old Family Blend, Bayleef was one of the Pokémon Professor Oak sent to Ash and Bayleef tackled Barry when it got separated from Ash. However despite being called up, Bayleef didn't take part in the Lily of the Valley Conference.
|Razor Leaf +||The Chikorita Rescue|
|Vine Whip||The Chikorita Rescue|
|Tackle||Chikorita's Big Upset|
|Sweet Scent||Gettin' the Bugs Out|
|Body Slam||Turning Over A New Bayleef|
|Headbutt||Playing With Fire|
|+ indicates this Pokémon used this move recently.*
- indicates this Pokémon normally can't use this move.