Keegan is a character from "The Stolen Stones!" (EP192) who runs a courier business with his older sister Ramona and their Arcanine. The siblings were in the middle of delivering Fire Stones for an upcoming Fire-type competition when they stumbled across Ash and his friends trapped under a rock-slide and rescued them. Grateful, they offered the group a ride on Arcanine toward a city near Olivine City.
Seeing Ash's interest in their Pokémon, Keegan tried teaching him how to ride and command Arcanine—though Ash struggled with it at first. Before they could make much progress, Team Rocket stole the Fire Stones they were supposed to deliver.
Keegan and Ash chased down Jessie, who agreed to return the stones if Ash beat her in battle. Pikachu made quick work of her Arbok, but when they went to collect their prize, they fell into a trap and discovered the stones were fakes. Keegan hurt his arm in the fall, which became a problem when they needed to go after Jessie again—he couldn't handle Arcanine with his injury. Ash stepped in to lead the Pokémon instead, and with Keegan's advice to "become one with Arcanine" the same way he was with Pikachu, Ash finally got the hang of it.
The group tracked down Team Rocket, recovered the real Fire Stones, and Keegan and Ramona successfully completed their delivery to the competition.
Content compiled by AnimeList.moe from publicly available sources.