You have to have (buy) the action replay game pack.
Once you have it you can get a mew, mew 2, & even a mew 3 (which by the way is extremely cool), unlimited master balls, & much more.
Chat with our AI personalities
You can't get a Mew unless you cheat, I think. A Mewtwo you can only catch in Fire Red\Leaf Green and transfer to your Pearl.
There is no Mew in Fire red/Leaf green
There is none. all cheats for getting a mew are as fake as Micheal Jackson's nose
give me god sword
Some people say to nickname your starter Pokemon "Mew" and it will play as mew for the rest of the game but I never tested it...