Clauncher first appeared in JN138, when he grabbed Ash's Pikachu's tail with his pincer. Corphish came to his defense, and after a quick scuffle Ash decided he wanted to catch the Water Gun Pokémon. However, he was stopped by Misty, who also wanted to catch him, giving Clauncher a chance to flee. Misty then revealed that she had fished up Clauncher earlier and decided that it was fate that she capture him, having tried and failed multiple times already. Unable to decide who deserved the chance, the two decided to fish for him and see who reeled him in first. Both were able to hook him, but unable to reel him in, so Clauncher suggested the two battle for the right.
Before they could start, however, Team Rocket hooked Clauncher with the intent to eat his meaty claw. Corphish was able to free him, and together they sent the evil trio blasting off. Afterwards, the battle was held between Corphish and Misty's Politoed. Misty won the battle, and as such, Clauncher allowed himself to be caught by her. After being caught, he let himself out of his Poké Ball in order to train Corphish on how to better use Crabhammer.
In JN141, Clauncher was called out alongside Psyduck and Politoed to help the Squirtle Squad stop a rampaging fire.
Clauncher has a lot of spirit and love for battling, as well as respect for those who can battle. This was shown with his respect for Ash's Corphish, as well as deciding that whomever was the better battler would be his Trainer. He has a slight mischievous nature as well, toying with both Ash and Misty when they were trying to reel him in.
Clauncher and Corphish grew to have a close bond in the short time they were together, sharing a mutual respect for their skills, their battle prowess, and their big claws. This was further shown after his capture, when he released himself from his Poké Ball to give Corphish pointers on how to improve his Crabhammer over celebrating with Misty.
Despite this one moment, Clauncher seems to have completely accepted Misty as his Trainer. When Misty won the battle for him fair and square, he willingly allowed her to capture him and became her Pokémon. As shown in JN141, he loyally follows her commands without hesitation.