During Pokémon’s original series, there was a certain character who would frequently appear but decreased in relevance over time. It was the Magikarp salesman. He appeared a lot in the original series but only made a handful of key appearances between Advanced Generation and Diamond and Pearl. From there, he only ever made two more cameos — Black & White and Journeys.
It’s a mystery why exactly the Magikarp salesman fell off so drastically. Even Jigglypuff, a similarly forgotten character, got a minor role in the Sun & Moon anime after disappearing in Advanced Generation. However, it might be possible to come up with some reasons based on the context in which the Magikarp salesman appeared and disappeared.
Why Did the Magikarp Salesman Disappear?
The Magikarp salesman likely stopped showing up because people had no further reason to keep falling for his scams. The only way he could get Team Rocket to fall for his tricks by the Advanced Generation series was by insisting he was a changed man, and even that raised some eyebrows. The one other time they fell for his scam was in Diamond & Pearl Episode 21, “Ya See We Want An Evolution!,” after which he ran off and never showed himself in front of them again. As for Ash and Co., they were never foolish enough to fall for his scams to begin with. Thus, he would have to look elsewhere if he wanted to continue conning suckers out of their money.
It’s also worth noting how many of his appearances were relevant to the anime’s overarching plot. He was directly responsible for Jessie trading her Lickitung for Wobbuffet and James losing his Victreebel. He was also in the episode where James obtained a Chimecho, although his role on that front was minimal. As Team Rocket found new means to gain and lose Pokémon, the Magikarp salesman became less necessary as an impetus.
The Magikarp salesman also only appears in episodes helmed by specific writers, namely Yukiyoshi Ohashi. He’s responsible for every episode that featured the Magikarp salesman. Incidentally, the two episodes where he made cameos were written by Atsuhiro Tomioka. It’s likely that since Ohashi was involved in fewer episodes following the original series, there were fewer opportunities for him to include the Magikarp salesman.
If the Magikarp salesman ever shows up again, it won’t be any time soon. He’d need main characters dumb enough to buy his products, Ohashi or Tomioka writing the episode, and possibly a lasting reason for said main characters to gain or lose a Pokémon besides the one he’s selling. Unless those conditions can be met, he’ll likely remain on his indefinite hiatus from the show.