Pokémon X and Pokémon Y

I see.
So Mewtwo get's smaller, because when he gets stronger, he becomes more like the original pokemon that created it.
I just find getting smaller when you get stronger an illogical concept, because like @Lozmaster pointed out; it almost never applies to pokemon...
I also don't get what, Mewtwo transitioning from a man-made pokemon into it's own species, and therefore looking more like a pokemon and less like a human, has to do with me using buu and mewtwo as an example to point out that I find getting smaller when you get stronger is an illogical concept...

Logic doesn't necessarily apply in pokemon. need we remind you of Hot Skitty on Wailord Action.

It has everything to do with Mewtwo becoming a "real" pokemon. It wasn't a true pokemon because it was manufactured and thus had limitations due to how it was created, by "awakening" and bypassing those limitations it becomes what is basically a real pokemon. Like in Jurassic Park where the dinosaurs are manufactured by scientists, and are therefore not meant to exist. They are unable to breed but they find a way, because life finds a way. the same applies here.

Mewtwo becomes smaller because it becomes more like Mew. Saying that something can't become smaller and more powerful is denying the existence of already small but powerful pokemon like Mew, Celebi ect.

saying "it almost never applies to pokemon." is silly. we didn't have fusion until the last gen, then comes along White and Black Kyurem.

And like with the case of Buu, there are lots of examples of things becoming more powerful and decreasing in size in tons of media, especially in Japan. in anime, games, JRPG's especially.

There is always a base form (Mew), an imperfect and monstrous form (Mewtwo) and then a perfect form (Awakened Mewtwo) it's just how these things work.

I mean hell, if we are using DBZ references, there was also Freiza and Cell, who did the EXACT same thing.