Talk:Mewtwo/@comment-79.144.59.218-20120428225156/@comment-82.113.119.74-20120428233226

God guys, when you use a site such a wiki which has a comment function, then spend a couple minutes on reading the WHOLE post and at least the latest comments or use the search function of your browser. Here the most recent comments already are shown on top. Only seven posts under your question you find an exact answer given just 3 hours ago:

Nope. Mew and Mewtwo just randomly appear in the waves along with all the other Pokemon in the Unknown Dungeon level. They both are regular (not boss) and you catch them like every other pokemon in this game by damaging them till the health bar turns red and throwing your pokeball then.

You just need to be patient and make sure to bring a Gengar to get Mew/Mewtwo low enough in order to catch them.