The Magikarp Salesman, inspired from the one in the Generation I games, is a character who sells primarily Magikarp or Pokémon meant to fool his customers. He is first seen in the Kanto region.
In the anime, he has appeared numerous times, selling James and Jessie Pokémon that are actually ripoffs.
In the games, he sells Magikarps for 500 Pokédollars at the Pokémon Center near Mt. Moon.