Update 1/19/2019: Please click here for an updated list of Pokemon that are still missing in Pokemon GO, including Gen 4 Pokemon.

When Mew was finally added to Pokemon GO as part of the first Special Research quest, it meant that players could finally complete their Kanto region Pokedex (assuming they were willing to do a bit of globe-trotting to catch the region exclusives). However, at the time of this writing, it's currently impossible for anyone to complete their Johto or Hoenn Pokedex, as there are still some Pokemon are that are simply missing from the game.

Here are all the Pokemon currently missing from Pokemon GO, and the likely reasons why they have yet to be added to the popular mobile game.

Generation 2 - Johto Region

Generation 2 is currently missing two Pokemon in Pokemon GO. The first is Pokedex 235, Smeargle, which is a normal-type Pokemon. Smeargle's move is Sketch, which allows it to use whatever attack was just used by its opponent. This would allow Smeargle to learn every type of move in the game, in turn making Community Day exclusive moves less special. Smeargle's unique Sketch move seems to be the most likely reason why it has yet to be added to Pokemon GO, but Niantic will likely think of a way to incorporate it into the game at some point.

The only other second generation Pokemon that's not available in Pokemon GO is Pokedex 251, Celebi. Since Celebi is a mythical Pokemon, it's likely that it will only be available as part of a Special Research quest, but that's just speculation at this time.

Generation 3 - Hoenn Region

At the time of this writing, there are 13 third generation, Hoenn region Pokemon unavailable in Pokemon GO. This includes Pokedex 290 Nincada and its evolution line, Ninjask (Pokedex 291) and Shedninja (Pokedex 292). The likely reason why Nincada, Ninjask, and Shedninja have yet to make it to the game is due to Shedninja's Wonder Guard ability, which makes it take zero damage unless a super effective move is used against it. It seems as though Niantic has yet to decide how exactly to handle this ability, but an easy solution seems to be just to keep it the same, but make Shedninja too weak to use effectively outside of gym battles.

Pokedex 327 Spinda also has yet to be added to Pokemon GO. Unlike most of the other Pokemon listed here, there isn't a strange ability or mythical status keeping Spinda from being in the game. On the contrary, Spinda's gimmick of having unique markings, with an extremely low chance of players having one that looks identical to another, is likely keeping it from being added to Pokemon GO.

Pokedex 352 Kecleon isn't in the game because it's invisible most of the time, and its Color Change ability changes its type to whatever move it's being attacked with. However, like Shedninja, it seems as though Niantic could include this odd ability in the game as long as it's balanced properly. As for Kecleon's invisibility, those who have managed to complete the Special Research quest and catch Mew should have tech in-game that allows them to see invisible Pokemon, so many players should technically already have the means to catch Kecleon.

Like Kecleon, there are likely two reasons why Pokedex 366 Clamperl has yet to be added to Pokemon GO. Clamperl can only be found at "the bottom of the ocean," so Niantic may not have decided how to make it appear in the wild just yet. Secondly, Clamperl needs the Deep Sea Tooth to evolve into Huntail, and the Deep Sea Scale to evolve into Gorebyss - two evolution items that Niantic will also have to add to the game at some point.

The rest of the gen 3 Pokemon that have yet to make it to Pokemon GO aren't in the game yet because they are legendary and mythical Pokemon. Pokedex 377 Regirock, Pokedex 378 Regice, and Pokedex 379 Registeel all fit into the legendary category, whereas Pokedex 385 Jirachi is a mythical Pokemon, as is Pokedex 386 Deoxys is as well. However, datamining efforts have shown that Deoxys will likely come to the game soon, so players have that to look forward to.

Of course, every fourth generation Pokemon has yet to be added to Pokemon GO, and that goes for generations beyond that as well. At the rate Niantic has introduced new generations to Pokemon GO, it may be years before the mobile game manages to catch up to the core releases, so fans should have no shortage of new Pokemon to look forward to.

Pokemon GO is out now for iOS and Android mobile devices.

Source: Pokemon GO Hub