just beat the elite four
There's nothing left for you to do.
You can't catch Mewtwo on XD, Colosseum, Ruby, Sapphire or Emerald. Mewtwo can be caught in the Fire Red or Leaf Green Version then traded over to Emerald, Ruby, Sapphire, Colosseum or XD.
Try to catch it with a masterball. that's what i did.
No trade one from firered or leafgreen.
Throw a Master Ball at it.
Go buy a red or blue version. Catch a mewtwo. You'll instantly be cooler than all your friends.
Mewtwo is a legendary psychic type of Pokémon. Gary does not appear again after you catch Mewtwo in Pokémon Leaf Green version.
Cerulean Cave, Deepest point.
You catch mewtwo in the curlean cave.
VICTORY ROAD you have to posion him or somthing like put him to sleep I know I have Moltres, Articuno, zapdos, and mewtwo. juliez1:you should use ultra balls
Three legendary birds - Moltres (fire) Articuno (ice) and Zapdos (electric) and also Mewtwo. There is a glitch which allows you to catch Mew but this may affect your game.
In Pokémon SoulSilver, Mewtwo can be found in the Cerulean Cave but you will not gain access to it until you have defeated Blue.