Hang on one minute.

[AZ Jr]

If Mewtwo is a clone of Mew, how is it that Mewtwo comes before Mew in the Pokédex? MIND BLOWN.

 

[moon]

If Mewtwo is a clone of Mew, how is it that Mewtwo comes before Mew in the Pokédex? MIND BLOWN.

I always found that weird too xD But the explanation I heard is that Mew was originally not meant to be a pokémon possible to find in the games. Just a mirage, a legend leading up to Mewtwo. In a late stage before the release, they added in Mew anyways and thought up an event for it to be distributed. In the pokédex, it became #151 because it was added last. Maybe it was simpler that way.

Outside of the games, you could maybe explain it with the professors deciding the order in the pokédex finding out about Mewtwo before they got proof that Mew still existed in this world? The fossil pokémon are in the pokédex too, but they could be resurrected (without weird superstrength clones) so that's not so weird.

 

[Nah]

It's probably because Mew was never originally intended to be in the games. Mew was only put into the games about a week or so before their release. One of the programmers noticed there was just enough space left in the games' for one more Pokemon, so as a sort of joke they slipped Mew in. But since Mewtwo was already in place, Mew came after Mewtwo.

Mew's development was not overseen by Ken Sugimori, but by Game Freak programmer Shigeki Morimoto. Morimoto programmed Mew into the game secretly, as a prank amongst the staff just prior to its release in Japan, intending it to be a Pokémon only Game Freak staff members would know about and be able to obtain.[1] Mew was added at the very end of the development of Pokémon Red and Blue after the removal of debug features, freeing up just enough space to add the character despite being told not to alter the game any further at this point. Though not intended by the developers to be obtainable, due to a glitch, players were able to encounter it.

 

[LavenderTownGhost]

Nice observation. xD What the above poster said.

They probably thought of the idea for Mewtwo first and then realized, "Oh yeah, we need a Mew One." Haha.

 

[ORegan]

It could also tie into when your character obtains the two Pokemon in question. Oak tasks you with finding all the Pokemon in the world region to gather information on all of them. If all the Pokemon where already known by Oak prior to sending you on his errand, then the entire ordeal would essentially be useless. In the games, you find Mewtwo in Cerulean Caves and ideally Mew after the fact(assuming you get Mew via event and don't use the "Mew glitch.") This would put Mewtwo's publicaly announced discovery ahead of Mew's despite the fact that the small group of scientists who use to inhabit the burned mansion had to obtain a Mew to create Mewtwo.

 

[AZ Jr]

While all these explanations are valid, would it really be that hard to swap two Pokémon's positions? Just so I don't keep staring at my Pokédex, slightly bothered. I guess it's not that important, it just makes limited sense.

Cut that first bit out, I'm going with ORegan's theory. Thanks.

 

[ORegan]

While all these explanations are valid, would it really be that hard to swap two Pokémon's positions? Just so I don't keep staring at my Pokédex, slightly bothered. I guess it's not that important, it just makes limited sense.

Chalk that up to tradition. Another thing that they should correct from the Gen I dex is that Nidoran M and Nidoran F are counted as two different Pokemon, and not gender specific formes. Meowstic shows that the two genders of the same Pokemon can have different BST's, so in my mind, there is 150 Pokemon in RBY even including Mew.