Ash's Bayleef/Anime/History/OS

Bayleef debuted in The Chikorita Rescue as a Chikorita. Chikorita was especially stubborn, going so far as to fight Ash's Charizard despite obvious overwhelming odds, and was injured in the process. kidnapped her and tried to convince the stubborn Pokémon to join them, but Ash eventually won her confidence by saving her from Team Rocket.

Chikorita was used in Once in a Blue Moon to try getting the GS Ball back. However, Chikorita only wanted to be affectionate, so when got near Ash, Chikorita got angry and tried to hit it with her leaf but accidentally hit Ash instead. and noticed her affection toward Ash, leading Brock to speculate that she had developed a crush on Ash.

Chikorita made her Gym debut in Fighting Flyer with Fire, where she took on Falkner's. Ash showed that he believes in Chikorita by defending his choice to a disapproving Falkner, but Chikorita was outclassed by the, who dodged her Vine Whip and and then knocked her out with a  and a Tackle.

Chikorita's jealousy of and resentment towards Ash arose in Chikorita's Big Upset. Ash tried to withdraw Chikorita for Pikachu in a battle with a Trainer's, but Chikorita would not allow this and the battle was suspended by the time Ash returned her. She later ran away during the night and stumbled into the territory of a group of urban Pokémon. Lashing out at the, she knocked it out and became the new leader. Team Rocket tried to take her and the other Pokémon with their robot made out of tires, but Ash risked himself to save her, and Chikorita returned the favor by catching him when he fell. The two then took down the robot and Chikorita forgave Ash and became friends with Pikachu.

In Gettin' The Bugs Out, Ash used Chikorita as his second Pokémon in his Azalea Gym Battle despite the type disadvantage, something which Bugsy mocked. She went up against. After dodging some s she used Vine Whip, which Spinarak was able to dodge by aiming String Shot at a tree. Chikorita launched multiple Vine Whip attacks, all of which were dodged by Spinarak who used the trees to dodge. Her Razor Leaf and Spinarak's Poison Sting collided and destroyed each other. Chikorita then used Sweet Scent to distract Spinarak and then she defeated it with Tackle. She then went up against, Chikorita used Vine Whip but Metapod countered with , and Vine Whip didn't faze Metapod. The same thing happened with her Razor Leaf. She used Razor Leaf again but Metapod jumped and used Tackle, knocking Chikorita out.

In The Totodile Duel, Chikorita defeated Misty's Staryu in a battle to determine who got a wild. She was almost defeated by the powerful, but she dug in her heels and then managed to dodge a Tackle and hit Staryu from behind with Vine Whip. By this point, she had proven to increase her battling capability significantly, taking down Jessie's Arbok in a single Tackle in The Heartbreak of Brock. In Current Events, Chikorita evolved into Bayleef to protect Ash from Team Rocket. However, in the following episode, Turning Over A New Bayleef, the amorous Pokémon was shown not to have realized she had grown so much and continued to act as though she was still small enough to leap into Ash's arms. This problem was addressed when she ran away after Ash scolded her to "get away and stay away". Bayleef then came across Haruno and her Pokémon, and she and Ash made up in the process of taking down Team Rocket's giant Bayleef mecha. After the villainous trio had been defeated, Bayleef showed her affection towards Ash by using her newly learned Body Slam on him.

In Ash's Gym battle against Chuck in Machoke, Machoke Man!, Bayleef single-handedly won Ash the Badge after Pikachu's defeat to. She bested Poliwrath in a display of strength, slamming Poliwrath to the ground with a Vine Whip and then using Body Slam to knock it out. She then fought Chuck's powerful, taking damage from and , but showed good strategy by restricting Machoke's arms with her vines to block his , and then used her own Submission-induced momentum to in turn slam Machoke to the ground. She then used Body Slam and a point blank Razor Leaf to take out Machoke and win the battle.

She was briefly sent back to Professor Oak's lab in Dueling Heroes in exchange for his, who Ash needed to compete in the Whirl Cup. She did not warm up to Oak well, and Oak called Ash to inform him that Bayleef was restless. Finished with Kingler, Ash returned Bayleef to his team in the next episode.

In Extreme Pokémon!, Bayleef participated in the Extreme Pokémon Race with Ash, racing Gary Oak and his. She showed an immense feat of strength by hurling Ash at Team Rocket's balloon so that Ash could pierce it with his skateboard and rescue Arcanine. She then arrived just in time to attack Jessie's and hold it off long enough for Gary to catch up, who took down Arbok with his Arcanine. Bayleef and Ash worked together to finish the race and they managed to best Gary just at the end, winning the race for Ash.

It was the only member of his then-current team to make up Ash's team of six against Gary Oak. In Can't Beat the Heat!, she was sent out to give Ash a type advantage over Gary's powerful, managing to use Vine Whip to jump above. However, her aerial Razor Leaf was deflected by a, and she was knocked out when Blastoise her leaf and tossed her aside. She redeemed this loss in Playing with Fire!, in a battle with 's, again showing innovativeness by clamping Houndoom's jaw shut with Vine Whip and then using Body Slam to take it down. She put up her best efforts against, but was unable to overcome another type disadvantage and was defeated by.

Ash left Bayleef at Professor Oak's lab before he departed for the Hoenn region.