You can't. the only way is by the use of an event which has long passed.
no because there isn't a mew-three just mew and mew-two sorry
Mew does not evolve, Mewtwo is a completely different pokemon.
there is no events in Pokemon emerald but you can catch it after you beat the elite four then go to the second Pokemon gym and there should be a cave with a guy standing in front of it and mew and mewtwo should be in there hope i helped
You can't catch Mewtwo on XD, Colosseum, Ruby, Sapphire or Emerald. Mewtwo can be caught in the Fire Red or Leaf Green Version then traded over to Emerald, Ruby, Sapphire, Colosseum or XD.
No you cant get Mew on leaf green, but you can get Mewtwo in Cerulean Cave.
a
Mew can't be catched in Pokemon heartgold, only mewtwo.
You can't catch Mewtwo in-game in Pokemon Diamond.
No you cant you can only get mewtwo in the kanto reigon
You need to trade Mew from Emerald
Only if you have a code breaker and the master code for ruby plus the mew and mewtwo code
Mewtwo, Zapdos, Moltres, and Mew.