Yes, he is catchable. First, beat the elite four, then find the ruby and sapphire in the sevii islands and return them to Celio. Once they are given to him, go to Cerulean Cave (the cave in cerulean city), it should no longer be blocked by a man. Search the cave until you find Mewtwo. You will need RockSmash and Surf. He will be lvl 70.
The catchable legendaries are the following: Articuno, Zapdos, Moltres, Raikou/Suicune/Entei *depends on your starter pokemon*, Mewtwo.
*Mew is not catchable in Pokemon x and y, but you can get him online from wondertrades and such. Mewtwo however, is catchable and you can find him in the cave in pokemon village.
Mewtwo is found in cerulean cave.
trade it from red,blue, or yellowMewtwo is not catchable in the wild in Pokemon Crystal.
No you can not
Mewtwo!
g46bhcgcxdh
Unowns are only catchable in firered and leafgreen trade one to emerald to have it.
no, firered or leafgreen
Mewtwo.
trade from firered or leafgreen.
Mewtwo? Plus you cannot get Mew in Leafgreen or Firered.