Buizel in his debut appearance
On their way to Eterna City, Ash and his friends heard of a very strong Buizel that was able to defeat any opponent. Both Ash and Dawn had become interested and wanted to catch him themselves. Dawn was the first to catch this Buizel on her fishing line. She sent her Piplup to battle him, but Buizel proved to be too fast and too strong for Piplup to handle. The same would happen to Zoey and her Glameow, who were the second to go against him. Ash was the last to battle him with his Pikachu, and he was able to cause serious damage to Buizel. Ash made an attempt to catch him, but he escaped from his Poké Ball. He then went on to defeat Pikachu, and then took the group's fishing rods away.
Later on, the group met up with Buizel again and tried to get involved in his special training so that they could prove their worth to him. While this happened, Buizel grew attached to Ash. During this time, Team Rocket made their attempt to try and steal Buizel by catching him in a net. Though Ash was able to cut the net loose from Team Rocket's balloon, Buizel was plummeting towards the river still trapped in it. Luckily, Dawn was able to save him before he struck the water at full force. Because of what she did, Buizel decided to give Dawn another chance at battling him. This time, she and Piplup were victorious, and Dawn made her capture.
In the next episode, the group had met up with Elite Four member Lucian in a Pokémon Center after Buizel had injured Ash's Turtwig in battle. Sensing Lucian's status as a great battler, Buizel was very excited to get a chance to go up against his Pokémon and challenged him. Like in the battle against Ash's Turtwig, Buizel preferred to do things his own away, and ignored most of Dawn's commands. Because of the lack of cooperation between Trainer and Pokémon, Lucian's Bronzong proved much too powerful, even for Buizel's standards, and he was defeated. Afterwards, he fell into a depressive state, not being able to handle defeat so well. Lucian had explained that Buizel needed to learn how to handle being defeated and regain his battling spirit. During another scuffle with Team Rocket, Buizel gained a bit of his confidence back and was able to escape their grasp. Lucian then wanted to show Dawn how to use Buizel's unique battling style by taking command of him himself, and using him to defeat the trio. Afterwards, Dawn started to understand Buizel's battle methods, and wanted to help him develop his personal style, rather than force him to use another.
In A Stand-Up Sit-Down!, Buizel's abrasive attitude scared Zoey's Shellos, prompting Piplup to reprimand him. The two started arguing and Dawn had to restrain them. Seeing the situation, Zoey asked how Dawn was planning to compete in a Double Performance event with Pokémon that do not get along very well. After learning about Double Performances and being informed that the Pokémon Contest scheduled to be held in Hearthome City would feature them, Dawn decided to pair up Buizel with her Buneary in order to work on a new kind of technique for them to use. She came up with an improvised move known as "Ice Aqua Jet", in which Buizel, while using Aqua Jet, would be frozen by Buneary's Ice Beam, making him look like an icicle, but her plan was unsuccessful. Dawn did hope to perfect it before the Hearthome Contest, where she planned to use Buizel in the Battle Stage. However, before he could even be used in Dawn's Early Night, Dawn discovered that she had failed to clear the Performance Stage, leaving Buizel's Contest debut to be put on hold.
Buizel would later be used in the Hearthome City Tag Battle Competition in Smells Like Team Spirit!, where Dawn had made it to the final round with her Tag Battle partner, Conway. He would be paired up with Conway's Heracross, while his opponents were Ash and Paul, who were using Chimchar and Elekid, respectively. Buizel and Heracross's team up was an almost unstoppable force, and victory seemed to be within their grasp. However, Paul's Elekid evolved into Electabuzz during the battle, which helped it and Chimchar gain the upper-hand. In a very close battle, both Buizel and Heracross were defeated.
In Throwing the Track Switch, Dawn began the Contest training for the Solaceon Town Contest; however, Buizel seemed to be more interested in Ash's battle training, and thus couldn't set his mind on Dawn's training. Meanwhile, Ash's Aipom appeared to have a similar problem in Ash's training, because her moves tended to be more Contest-oriented. Then, Zoey proposed that Ash and Dawn trade them. Dawn initially wasn't sure, because Ash had a close bond with Aipom, but Zoey pointed out that Buizel seems to be forced into Contests. After more soul-searching, it was suggested that Ash battle Brock with Buizel and Dawn battle Zoey with Aipom. This led to an encounter with Team Rocket, after which the Trainers agreed that a trade was for the best, and the trade took place afterwards.
In A Triple Fighting Chance!, he faced off against Maylene's Lucario during Ash's Gym battle at the Veilstone Gym. Their battle ended with a double knockout, resulting in a tie between Ash and Maylene. During the battle, Buizel learned Water Pulse. Buizel's version is unique, as Buizel's Water Pulse retains its spherical shape, which is presumably inspired by the Aura Sphere of Maylene's Lucario. Buizel also revealed his Ability, Swift Swim, for the first time, which became critical to Ash's performance.
In Staging a Heroes Welcome!, Buizel participated in his first Pokémon Contest, as Ash's entry for the Wallace Cup. In the Performance Stage, Buizel managed to impress the panel of judges by showing off his unique characteristics, such as his swimming skills and the flotation sac around his neck. The performance secured Ash's progression to the Battle Stage. In Pruning a Passel of Pals!, Buizel defeated a Kecleon in his first match, but lost to Kyle's Lanturn in his second match. During the competition, Buizel perfected the Ice Beam and Aqua Jet combination that Dawn had tried to teach him in an earlier episode.
In A Crasher Course in Power!, Buizel was training for Ash's Gym battle at the Pastoria Gym, and was accidentally shocked by Pikachu. Buizel angrily jumped at Pikachu, but was restrained by Turtwig. Buizel continued to hold a grudge against Pikachu during the battle. Buizel defeated Crasher Wake's Quagsire using his "Ice Aqua Jet" combination, and stayed on to battle Floatzel. Floatzel managed to use most of Buizel's attacks against him, and eventually confused him with his own Water Pulse. Buizel was recalled, and Pikachu was sent out. Buizel eventually shook off the confusion to see Pikachu valiantly fighting a losing battle against Floatzel. Floatzel eventually partially froze Pikachu's back, and Buizel wanted to get back in the fight. As Pikachu and Buizel tagged out, they exchanged a high five, and Buizel broke the ice on Pikachu's back with a Water Gun. Buizel went on to defeat Floatzel by using a Water Pulse at close range, defeating Floatzel and earning Ash his Fen Badge.
Ash and Buizel in the Hearthome Gym
In Shield with a Twist!, Buizel was the first Pokémon that Ash sent out during his battle at the Hearthome Gym, going up against Fantina's Gengar. Buizel used Aqua Jet, but Gengar used its Levitate Ability to easily dodge and confuse Buizel with its movements, after which he missed his Sonic Boom attack. Gengar then used its Ghost-type movements to confuse Buizel again and hit him with Shadow Punch, which Buizel was unable to dodge. However, Ash was prepared for Gengar's Hypnosis, getting Buizel to create a Water Gun barrier to block Hypnosis and trap Gengar, with Fantina calling it a Counter Shield. After a clash of Gengar's Night Shade and Buizel's Water Pulse, Gengar was defeated. Buizel was then recalled, before he later went up against Drifblim. He used an Aqua Jet Counter Shield to extinguish Drifblim's Will-O-Wisp Counter Shield and damage it in the process. However, it then countered with Ominous Wind and Buizel's Water Pulse was countered by Will-O-Wisp. This allowed Drifblim to get close and use Hypnosis, putting Buizel to sleep. He was then defeated by Psychic.
In Dealing With Defensive Types!, he was used in battle against Byron's Steelix, but he could only use his Water Gun attack, which was easily countered by Steelix's Screech. The Iron Snake Pokémon, having Buizel unable to move due to the loud noise, trapped him with Bind, threw him into the air, and defeated him with an Iron Tail since he was unable to dodge, slamming him to the ground. When the dust caused by the impact cleared, Buizel was still standing, but ultimately collapsed, and was unable to battle.
In Pedal to the Mettle! and Evolving Strategies!, Buizel was the first Pokémon used by Ash in his Full Battle against Paul. However, he was immediately recalled by Ash when Paul chose to start with his Torterra. Buizel was later sent out against Paul's Magmortar, but despite the type advantage, he struggled against the Blast Pokémon, and was poisoned by its Smog before Paul recalled it. Paul then sent out his Ursaring, and Buizel again found himself up against a stronger opponent. Nevertheless, Buizel put up a good fight, and was able to use his Counter Shield technique to hurt Ursaring. When Buizel started to lose strength, Ash wanted to recall him; however, the Sea Weasel Pokémon requested to stay in the battle, and Ash agreed. This proved to be a mistake, as Buizel was instantly knocked out by Ursaring's following Focus Blast.
In Short and To the Punch!, Buizel battled a Mr. Mime belonging to Clayton and lost, which eventually led to Buizel learning Ice Punch. In battle, Buizel's Ability Swift Swim activated once again.
In Flint Sparks the Fire!, Ash used Buizel in a battle against Flint's Infernape, but lost easily to a Flare Blitz, despite the type advantage.
In Four Roads Diverged in a Pokémon Port!, he trained late at night with Ash, and formed a rivalry with Kenny's Empoleon after having his own Sonic Boom attack hit back at him. The next morning, Buizel battled Empoleon and lost, despite putting up a good fight.
In Familiarity Breeds Strategy!, Buizel was brought out to battle Paul's Gastrodon. Buizel was able to use Ice Aqua Jet, and managed to finish off Paul's second Pokémon with Ice Punch, leaving Paul with four Pokémon, while Ash still had all six of his. Buizel stood in to fight Paul's Drapion, and despite using his own Counter Shield, he was caught off guard by Drapion's power and flexibility, which led to him being Ash's first Pokémon to fall in the battle.
Ash left Buizel at Professor Oak's Laboratory when he decided to go to Unova.
Buizel was reunited with Ash in The Dream Continues!, where he and the rest of Ash's Pokémon posed in a group photo with him.