In a series with over 900 Pokemon, it should come across as no surprise that a few Pokemon have been exceedingly rare, as far as the anime is concerned. Unsurprisingly, this list will primarily include Pokemon from the later generations, as those are the generations during which certain mons got less focus than the others. We have listed the 10 rarest creatures in the anime below.
Note: This list won't include Pokemon from Generation VIII (as they are too recent) or Generation IX (as the games didn't even come out by the time this article was written). It also won't consider alternate forms or Mega Evolutions, as it's still the same species for all intents and purposes.
Klang and Volcanion are among the 10 rarest Pokemon who are rarely (if ever) seen in the anime
#10 - Victini
Victini is one of several Pokemon on this list that only appears in the movies and specials. It was an important part of the 14th movie, and also appeared in the 26th Pikachu short. Victini's role in the latter was just to rescue Pikachu, while its role in the former was like other mythical mons before it.
The 14th movie has a trainer named Damon trying to take Victini to resurrect the Kingdom of the Vale. Ash and his friends help Victini out, and Damon's plans predictably fail as a result.
#9 - Klang
Bizarrely enough, Klang has never appeared in the traditional anime. Its pre-evolution and evolution did appear in a few episodes, making Klang's absence even stranger. There was no major controversy involving the Pokemon to explain its absence either.
Klang did appear in the 14th movie (along with its pre-evolution and evolution) in its most prominent role yet. The other two appearances include a brief cameo in the 23rd movie and a Black & White special episode.
#5~8 - Keldeo & The Swords of Justice
It would be repetitive to list Keldeo, Cobalion, Terrakion, and Virizion in separate entries considering that their roles in the series all involve one another. Basically, they all played a major role in the 15th movie, where Keldeo had to awaken its inner powers and fight Kyurem.
This group of mons has never appeared in the traditional anime series outside of that movie. In comparison, legendary trios from Gen IV and prior have all appeared in the series in one plot or another (some have also got movies of their own).
They haven't made physical appearances in any anime episodes, but their likeness was seen a few times with Virizion's silhouette appearing in a fantasy.
#4 - Volcanion
Unlike the previous entries, Volcanion doesn't get any cameos. To its credit, it had the benefit of being the star of the 19th movie, but that's it as far as anime appearances go. It seemed to hate humans at the beginning of the movie, but that hatred fades as Ash and company help it alongside Magearna.
The movie has a brief moment where it seems like Volcanion died, only to reveal that it barely survived. Like many of the Pokemon movies before the 19th film, all ends well for Volcanion and Magearna. The former is never seen in the anime again since then.
#3 - Porygon
Porygon's appearances in the anime outside of Japan have largely been limited to cameos, which isn't surprising considering how controversial Episode 38 of the original series was. It's an episode that never aired in the United States due to infamously causing seizures because of the scene where Pikachu triggers a flashing sequence of red and blue lights.
It wasn't Porygon's fault, but it did get the blame for it (after all, Pikachu was the mascot of the series). While it does technically have more appearances than some of the other entries on this list, it's obvious that it doesn't have much of a chance of ever making another appearance again.
#1~2 - Porygon2 & Porygon Z
Although these two Porygon evolutions are separate Pokemon, the fact of the matter is that they have never made a proper appearance in the anime (unlike Porygon). Their only appearance is in the 15th movie when every Pokemon (at the time) was briefly seen in a cameo.
Porygon2 suffers the indignity of debuting in Gen II yet never appearing in the anime in a non-cameo capacity. Its evolution, Porygon Z, is from Gen IV, and is yet to make an appearance as well.
Porygon was punished for sending several hundred kids to a hospital for symptoms related to a seizure, so it is not surprising that these two mons have never had a meaningful appearance in any capacity.
Note: This article reflects the writer's personal views.
Poll : Did you ever watch the banned Porygon episode?