Porygon only had 1 appearance in Electric Soldier Porygon (which never aired outside of Japan because almost anyone who watched it got seizures). Porygon2 also never appeared in the anime, except as a cameo in the Johto Pokerap.
Numel was only seen once, in the episode "Game Winning Assist" from the 7th season, Pokemon: Advanced Challenge.
Also, only a single Pachirisu appeared in the entire anime and it was Dawn's.
That's definitely the Porygon-line, but other then that... I'm not sure... I haven't seen Kadabra since "Fear Factor Phony" (it probably left to join SOVA...). Togetic is rather rare too.
Kadabra was probably left out due to the Uri Geller controversy.
Togetic has had only one appearance since when Misty released hers.
Also, the episode "Crossing Paths" from Pokemon DP: Battle Dimension was the only time a Dustox has been seen other than Jessie's (ironically, she released her Dustox in that episode).
The only Seviper to appear in the anime was Jessie's.
Time to talk about HO-OH!!!
Despite the provided background stories and explanations, the actual Pokemon (not the transformed Mew in Movie 8 nor the previewed one battling Lugia which techincally wasn't in the anime teehee) has only had about a ten seconds air-time, in like what, four episodes?
Oh yeah and then there are some of the movie intros.. and a four more seconds in Pop Goes the Sneasel..
Great fun rewatching For Ho-Oh the Bells Toll!
The only Ambipom to ever appear in the anime was Dawn's.
Now that she has sadly departed Dawn's team, no Ambipom has ever appeared since the 12th season (Galactic Battles).
I feel so sorry that Dawn's Ambipom was the only member of its species to ever appear in the anime.
Porygon2 and Porygon-Z have no appearances in the anime due to the "Electric Soldier Porygon incident" . Porygon-2 has a brief cameo in the Johto-Pokerap (Pokerap GS)
Yet somehow, Alakazam still gets to appear despite being very physically similar to Kadabra, lacking the star and the name etymology seems to be different in Japanese (being more of a Houdini reference or something along those lines). >.>
Interesting trivia about Dawn's Ambipom and her Pachirisu being the only members of their species to appear in the anime so far (goes to show how special Dawn is :cer_love:). Numel also seems to have only one appearance to its name, as a wild Pokemon (though there have been quite a few Camerupt appearances XD).
I guess Togetic's rarity stems from how Togepi was newly-discovered when we first saw it in the anime, being the second Johto Pokemon that debuted
way before Generation 2 even "existed" in the games.
Ho-Oh is an interesting case, being the first Johto Pokemon to debut in the anime way before Generation 2 properly debuted in the game series. Lugia has been seen
several times (one appearance even had it able to
breed another young Lugia). It's shrouded in so much mystery...even the advent of the recent
HeartGold/SoulSilver Versions didn't do much to help it out in appearances. At this point, Ho-Oh seems like it's being saved for a
very important anime appearance with Ash, or the writers just never got around to giving it much appearances aside from all the stories we've heard about it in recitation. Possibly the prime example of a legendary Pokemon actually befitting of the "very rarely-seen" attribute commonly ascribed to legendary Pokemon.
And the Porygon line...I feel so bad for them. :( The
Computer/
Electric Soldier Porygon (Episode 038) incident wasn't even Porygon's fault; Pikachu's Thunderbolt triggered the seizure-inducing effect. :x And most of them are reduced only to movie cameos, and Porygon-Z doesn't have an anime appearance
at all (though it does have existent anime artwork). So if you strictly watched/knew about only the Pokemon anime media up to the current, you would never even know that Porygon-Z
exists? Wow...
It's good that The Pokemon Company is paying attention to the sensitivity of EP038, although I wish that the Porygon line members all receive an actual, full-fledged appearance in the Pokemon anime television show someday... They're Pokemon, too (and unjustly misblamed, at that). :x