Clauncher first appeared in JN138 when grabbing Ash's Pikachu's tail with its pincers. Corphish came to their 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 it, 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 it, having tried and failed multiple times already to obtain it. Unable to decide who deserved the chance, the two decided to fish for it and see who reeled it in first. Both were able to hook it, but unable to reel it in, so Clauncher suggested the two battle for the right to capture it.
Before they could start, however, Team Rocket hooked Clauncher with the intent to eat its claws. Corphish was able to free it, 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 itself to be caught by her. After being captured, it let itself out of its Poké Ball in order to train Corphish on how to better use Crabhammer.
Clauncher has a lot of spirit and love for battling, as well as respect for those who can battle. This was shown with its respect for Ash's Corphish, as well as deciding that whomever was the better battler would be its Trainer. It has a slight mischievous nature as well, toying with both Ash and Misty when they were trying to capture it.
Clauncher and Corphish grew to have a close bond in the short time they were together, sharing a mutual respect for their skills and battle prowess. This was further shown after its capture, where it released itself from its Poké Ball to give Corphish pointers on how to improve its Crabhammer over celebrating with Misty.