How To Get More Than One Deoxy:

Get the aroura ticket to go to island 9 catch deoxy then get another gameboy,link cable,and fire red version and tranfer your deoxy to that game and trade a pokemon you don't want to leaf green and when you are trading the pokemon shut the game that is getting the weak pokemon off and then the one thats getting the deoxy and when you turn it back on the weak pokemon will be deoxy and you will have 2 deoxys.