No You don't.
To catch Mewtwo in LeafGreen or FireRed no. To migrate Mewtwo from LeafGreen or FireRed to Diamond/Pearl/Platinum yes you have to have it in Diamond/Pearl/Platinum.
To get Deoxys, you need the Aurora Ticket from a Nintendo Event. To get Latias, they are in the wild after you beat the Elite Four. To get Mewtwo, you need to trade from LeafGreen or FireRed.
You need to beat the Pokemon league. Prephare to face the leagendary Pokemon mewtwo in that cave. I recommend ultra balls.
first you bet the elite 4 and then go to ciolol and then you need to find the gems
Mew was distributed at an event once, but that is long over and sadly if you want a mew in leafgreen now, you'll need help from other games or you could use cheat codes.
Mewtwo is located at the same cave in firered/leafgreen, first, i recommand getting a level 70 or a bit above pokemon Then, you must get all 16 badges to enter, not sure if you really need that all Good luck capturing it! From: Jared
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.
ok if you want to know how to get mewtwo firstly all you need is Pokemon firered/leafgreen and capture mewtwo on that secondly you need the national dex thirdly need to beat the elete four (can't spell it) and fourthly some COMMON SENSE because all you do is migrate it you can migrate 6 Pokemon a day and you find 'em in the pal park or use action replay hope this helps ok if you want to know how to get mewtwo firstly all you need is Pokemon firered/leafgreen and capture mewtwo on that secondly you need the national dex thirdly need to beat the elete four (can't spell it) and fourthly some COMMON SENSE because all you do is migrate it you can migrate 6 Pokemon a day and you find 'em in the pal park or use action replay hope this helps
To Catch Mewtwo You Need A Action Replay.
Pokemon 150 is Mewtwo. It depends which game you're looking for answers for. If it is one of the DS games, you'll need to transfer Mewtwo over via Pal Park, as Mewtwo is available in LeafGreen and FireRed in Cerulean Cave. He is hard to catch but worth it.
you need to have gotten the ruby and sapphire and given them to celio on one island. after that the man in front of cerulean cave should have moved and you have gained entrance to the cave. you need HM rock smash to get through the cave. mewtwo should be in there. good luck :D
No, Mew and Mewtwo aren't in Diamond. To make a long story short: if you want Mew, you need to visit an event or you can trade/migrate it, but you still need to visit an event or you need an event item on your other game. If you want Mewtwo, you can trade/migrate it from FireRed/LeafGreen, HeartGold/SoulSilver or X/Y, or you need to visit an event with other games.