ANSWER 1:
Mewtwo appears only in Fire Red and Leaf Green. You can catch him in either of those games and then trade him to Pokemon Ruby.
sorry mate its impossible only way is to trade like this guy said (: (: (: (: (: (: (:
ANSWER 2:
I regret to tell you that you cannot catch Mewtwo in Ruby. You can only catch Mewtwo in FireRed or LeafGreen. (You can use cheats to get it but it wouldn't be as fun).
Mewtwo is at Level 70 in LeafGreen and FireRed so use an Ultra Ball/Timer Ball/Master Ball.
If you need/want a Mewtwo you can trade Mewtwo into your Ruby/Sapphire/Emerald Game.
Chat with our AI personalities
Only if you have a code breaker and the master code for ruby plus the mew and mewtwo code
how do you catch a mewtwo on Pokemon platinum
No you can't catch Mewtwo in Pokemon silver, you must trade it from Pokemon yellow.
Catch 'em all
1. you cant catch mewtwo on ruby emerald or saphire<spelling mistake> you can migrate the mewtwo you catch on leafgreen or firered to migrate to platinum