Keith was a thief who "accidentally" bumps into people, then switches their bags. His partner is Farfetch'd, who was believed it was weak in battles. When Ash and Misty battled it, Keith realized Farfetch'd was strong and promised not to steal any Poké Balls.
Farfetch'd was Keith's partner Pokémon in thievery. Though Keith believed Farfetch'd was weak, it proved to be quite a strong Pokémon.