From Bulbapedia, the community-driven Pokémon encyclopedia.
Keith (Japanese: キクマ Kikuma) is a character of the day of the anime who appeared in the episode The Evolutionary War!.
Keith lives on Island B, one of the A-B-C Islands. He prefers Huntail over Gorebyss. Because of this, he had a rivalry with Nancy, from Island C, who prefers Gorebyss.
When Team Rocket came by and tried to steal his and Nancy's Pokémon, Ash's Grovyle freed the Pokémon with Leaf Blade. Afterwards, they worked together to defeat the mecha and Team Rocket was blasting off. As a result, Keith and Nancy were finally able to end their rivalry with each other and waved goodbye to Ash and company.