Foster is the Gym Leader of Quaver Town's Gym, known officially as the Quaver Gym. He hands out the Snowball Badge to trainers who defeat him in battle. He specializes in training Ice-type Pokémon.
A jolly old man who has a gym full of children and teaches them about battling. He runs a daycare for preschool children in his gym and saves people in trouble around the icy roads of the mountain.
Foster's design draws inspiration from the traditional image of Santa Claus as a jolly fat man clad in red and white.
Foster is also the origin of the term "Foster Confirmed" used by the developers. The term refers to when a design is so overwhelmingly popular that it is assumed that it will appear in the final game, despite the fact that it may not be officially confirmed.
Foster's concept and design have not changed since they were first proposed.