Throughout the Pokémon series, there have been several non-Legendary species of which only one is available to the player, whether in the wild or through NPC interaction. Notably, some of these species become more common in later generations.
In general:
- Starter Pokémon. They can only be obtained as gifts from Pokémon professors and you're only allowed one per gameplaynote . Averted in Sun and Moon, where certain starter Mons like Squirtle and Totodile can be found in the wild, though they're still rather rare.
- Legendaries are typically only one per playthrough and found in dungeons that are both late in the game (or post-game) which have specific requirements to enter. Downplayed since, in later generations, legendary Pokémon can respawn either in their original location or a different location under specific circumstances, but they're still the same Pokémon regardless.
- This could be applied to some of the trainer classes as well, such as:
- The two (and only two, period) police officers in the second generation and their remakes, which can't be challenged to a rematch.
- In the fourth generation games, outside of the Battle Tower/Frontier, Roughneck Kirby is the only Roughneck trainer in the game.
- The Game Freak game designer and programmer Shigeki Morimoto has a Creator Cameo in Pokémon Black and White with the unique class of GAME FREAK, named after his employer.
Unique Pokémon by generation:
- Generation I:
- The three fossil Pokémon (Kabuto, Omanyte, and Aerodactyl) can only be revived with their fossils. And you only get to choose either the Kabuto or Omanyte fossil.
- There's only two Snorlax in the game, both of them blocking specific routes.
- You can only get one Eevee in a Pokéball in a building in Celadon City. Similarly, there's only one Lapras, which you are gifted in Silph Co.
- Farfetch'd, Lickitung, Jynx and Mr. Mime cannot be found in the wild and are only obtainable via in-game trades.
- You can only obtain Hitmonchan and Hitmonlee by defeating the Karate Master in Saffron City's Fighting Dojo, and you are required to choose only one.
- In Yellow, Pikachu is your starter, and cannot be encountered in the wild.
- In the Johto games, there's exactly one Sudowoodo you can fight. Snorlax is a Unique Enemy again as well, this time with only one instead of two, since Red has the other.
- Generation III:
- The only Beldum in the game is given as a reward for defeating Steven in the postgame.
- Chimecho is notable for not appearing ANYWHERE else in the game, aside from a single floor of a tower that the player is unlikely to spend more than a few seconds on.
- Generation IV:
- A single Spiritomb can be fought and caught at the Hallowed Tower on Route 209 in Diamond and Pearl and its Updated Re-release Platinum. Downplayed in that you can catch as many Spiritomb as you have Odd Keystones, but you're only guaranteed one, and Cynthia also uses one on her team.
- A straighter example is Rotom, of which only a single one can be found in the Old Chateau.
- There is only one single Wormadam in Diamond and Pearl, which is owned by a single, unremarkable trainer on the only route that you don't need to visit to beat the game. It doesn't appear in the wild either and can only be obtained via evolving Burmy. However, Platinum adds Wormadam as a possible enemy in the Battle Factory.
- Generation V: In Pokémon Black 2 and White 2, only one Darmanitan (formerly belonging to N) can be fought in the entire game, as the five from Black and White are no longer there.
- Generation VI:
- The Flabébé line appears with several different colored flowers, depending on where you caught it. The Dummied Out Eternal Flower Floette (which belongs to AZ, who brought it Back from the Dead), however, is completely unique, having both a different colored body (which is always the same on a player-caught Floette), and flower (both in color and shape). It is also the only Pokémon capable of using the move Light of Ruin.
- Just like in Diamond, Pearl and Platinum, you can catch a single Spiritomb in Sea Mauville in Omega Ruby and Alpha Sapphire.
- Generation VII:
- Although the player sees several of UB-01 Symbiont (a.k.a. Nihilego) during the story, the player is only able to capture one of them during the postgame. Likewise, fellow Ultra Beast UB-05 Glutton (a.k.a. Guzzlord) only appears once in the game, despite not being a Single Specimen Species. It's also worth noting that despite their power, Ultra Beasts aren't officially considered Legendary Pokémon.
- Although Pokémon Ultra Sun and Ultra Moon allows the player to catch infinite numbers of the original Ultra Beasts (and two of Blacephalon/Stakataka), Poipole is inexplicably only available as a gift from the Ultra Recon Squad. And since Ultra Beasts can't breed, the player can't even get more from this initial one unlike most other gift Pokémon. Note that Poipole is the Ultra Space equivalent of a starter Pokémon, of which only one is usually available and which cannot normally be encountered in the wild.
- Generation VIII:
- Averted for Charmander and more-or-less averted for the other original starters; while you're given a single Charmander in the postgame, and get to pick between a Squirtle and a Bulbasaur in the Isle of Armor, Charmander can appear in low-level Raid Dens if you know where to look, and the evolutions of all three can appear in higher-level dens and the Dynamax Adventures in the Crown Tundra.
- Also averted for any legendary that appears in the Dynamax Adventures; they can appear an unlimited number of times, though you can only actually catch (and keep) each one once. (This applies to the Ultra Beasts, who were not so limited in Pokémon Ultra Sun and Ultra Moon.)
- Poipole, however, is still unique. As are the usual regional starters, the Alola starter from the Diglett fanatic, the Slowpoke found at Windhurst Station if you don't have the DLC, and any legendary not found in Dynamax Adventures.
- You get one Gigantamax Melmetal, granted as a gift via sending any Pokémon from Pokémon GO to Pokémon HOME. Regular Melmetal cannot gain Gigantamax properties since the Max Soup feature in the Isle of Armor DLC predates GO connectivity with HOME, thus limiting you to one G-Max Melmetal.
- In Pokémon Legends: Arceus, only a single Overqwil can be found in the wild, an Alpha that appears inside Lake Valor's cave during the quest to create the Red Chain. More can be gotten by evolving Hisuian Qwilfish, but their absence otherwise is still noteworthy since one sidequest, which allows Manaphy and Phione to be caught, requires having an Overqwil in the party.
- Also in Legends: Arceus, you can get a single Alolan Vulpix from a late-game sidequest; every other Vulpix you can encounter in the game is the regular variant.
