Conditions:
-Get both Ruby and Sapphire Plates and have access to the unknown dungeon
-Unknowns !?
-Mewtwo
-Ditto
Once all conditions are done, put Mewtwo in your first slot, and have
ditto in the second, with Unknown ! being third, and Unknown ? being fourth.
Have a Pokemon that knows surf, and fly to island 6 and swim to the
transfermation cave after the forest. Once you enter, the ground will
start shaking and reveal a flight of stairs. Continue until you get to the
final room, where mew is. He is at level 30, so be careful.
it works , so do it!!