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 Pokémon Chronicles, he inadvertently attempts to do so at Professor Oak's lab, but Tracy catches on to his antics much faster than James did.
In the Generation III games Pokémon FireRed and LeafGreen Versions, he sells Magikarp for 500 Pokédollars at the Route 4 Pokémon Center, which is located near Mt. Moon.
Weepinbell → Victreebel