To catch mewtwo you need to have the ruby and saphire gems,  then go to cinnabar island and buy 99 ultra balls, then go to cerulean city you will need surf strength and rock smash then go up to cerulean cave and try to find mewtwo, when you have found mewtwo save the game and then talk to mewtwo and you battle it and it will battle you. mewtwo is a physic tipe pokemon.If you dont catch mewtwo if you have saved it before you battled it, you can just switch the gameboy  of and try a again.

 

matt