From Bulbapedia, the community-driven Pokémon encyclopedia.
Theodore (Japanese: タクゾウ Takuzo) is a character of the day who appeared in To Thine Own Pokémon Be True!. He made it to the finals of the Pokémon Ping Pong Tournament with his Gliscor and lost against O and his Shiftry. He did not have a speaking role in the episode and never appeared in person, but his face appeared on the screen showing the finalists.
This listing is of Theodore's known Pokémon: