TheGoldMan
Smash Journeyman
Here's a theory I have: Sakurai said the roster was finished before the game was revealed, and he said he was thinking of adding Mewtwo when a fan asked an X/Y developer if they would like to see Mewtwo in SSB4. If he was thinking about it, that means that he would either add him or cut him, because the roster was finalized along time ago. I doubt he would cut him twice, and he is a unique character and he isn't a clone of anyone. So yeah, that's my theory