Ash originally obtained Kingler as a Krabby in Mystery at the Lighthouse, when he became angry at Misty for saying that it was a fluke that he caught all his other Pokémon. Storming down to the beach, he discovered a minuscule Krabby and made fun of it. Krabby challenged Ash, who fought it with a nearby stick and then captured it in a Poké Ball. Having six Pokémon already in his party at the time, the newly caught Krabby's Poké Ball was immediately teleported away, much to Ash's surprise and concern. He soon learned that Krabby was sent to Professor Oak.
As a Krabby, being compared to Gary's bigger Krabby
Ash quickly rang Oak and was initially horrified at the thought that Oak was eating his new Krabby. However, the Professor pointed out that he was actually eating tofu. Ash's initial relief changed to jealousy after Oak also revealed that Gary had also caught a Krabby, although his Krabby was far larger in size. Later, in Showdown at the Po-ké Corral, Gary actually sniggered at the sight of Krabby's minuscule size.
Krabby made its battling debut in Round One - Begin!, when Ash used it during the first round of the Pokémon League against Mandi. He reasoned that Krabby would be perfect for a battle on the water field despite Misty's protests.
It seemed at first that Misty's forebodings would prove true; Mandi's Exeggutor used Psychic to trap Krabby in a whirlpool. However, Krabby managed to escape and took control of the battle with Vise Grip. It avoided Exeggutor's Hypnosis and took victory with Leer and Stomp. The intensity of the battle caused it to evolve into a Kingler. It was able to finish the rest of the match single-handedly, defeating Mandi's Seadra by slowing it down with Bubble and before knocking it out with Crabhammer; Kingler also defeated Mandi's Golbat with a Hyper Beam. This was despite Misty and Brock's real concerns about Kingler's ability to prevail against Seadra's speed and Golbat's air attacks.
Kingler, Muk, and Tauros offering to fight Drake
Ash also used Kingler in his battle on the ice field in Fire and Ice, where Kingler defeated Pete Pebbleman's Cloyster by striking its protective shell with a fury of unrelenting Crabhammers. It went up against his Arcanine, but its Bubble was dodged by the Fire-type Pokémon, and Kingler was knocked out by a Dragon Rage attack.
After realizing he only had one Water-type Pokémon, Totodile, in The Perfect Match!, Ash had Kingler rejoin his party in time for the Whirl Cup tournament. In the second round, after Totodile's loss to Poliwhirl, Kingler knocked out Poliwhirl with a powerful one-two punch Crabhammer. However, when Ash ordered it to use Vise Grip on Psyduck, the pain gave Psyduck the ability to tap into its Psychic powers and defeat Kingler with an overwhelming Confusion attack. Kingler was sent back to Oak's lab afterward.
In Love, Pokémon Style, Ash planned to use Kingler in the Johto League Silver Conference against Macy's array of Fire Pokémon, but it was injured while rescuing a trio of runaway Voltorb, who shocked Kingler when it caught them. Nurse Joy informed Ash that Kingler would need to rest up; luckily Squirtle arrived in time to fill Kingler's spot.
Kingler was reunited with Ash in The Dream Continues!, where it and the rest of Ash's Pokémon posed in a group photo with him.
Personality and characteristics
Kingler and Ash
In its debut, Krabby appeared to be fiery and brash, challenging Ash to a fight, despite him not even being a Pokémon. However, upon being caught, Krabby mellowed out significantly and became a very modest and quiet Pokémon. This is most likely due to its residence with Professor Oak, who said in Showdown at the Po-ké Corral that Pokémon take on the personality of the person who spends the most time with it.
In battle, Kingler was quite determined, not giving up against Mandi despite, at face value, being the underdog against all three of his Pokémon. Kingler was a very modest victor, happily hugging its Trainer, but not waving to the crowd or gloating at Mandi. These are more of Oak's traits coming through, as opposed to the rest of Ash's team. This is most likely the reason Kingler never secured a permanent position on Ash's team. It has proven strong in battle, loyal, and caring, but the very little time spent together has likely led Ash to feel more secure using his other Pokémon. Kingler, like Muk and Tauros, remains a trump card in Ash's arsenal.
Kingler is Ash's only Pokémon to win in a Pokémon League match single-handedly, excluding one-on-one matches.
Kingler was Ash's first Pokémon to evolve during a Pokémon League match, and the only one to do so before his Torracat evolved into Incineroar in Fiery Surprises!, 1,007 episodes after Kingler's evolution.
In Pokémon Yellow, a game highly based on the anime, Krabby's encounter rate is 70%, as opposed to Red and Blue's encounter rate of 33%. In addition, in Yellow only, it is possible to catch Kingler by fishing on Route 25. These additions of commonness are likely made as a reference to Ash's Kingler.