Mew is not able to be caught in FireRed/LeafGreen. Sorry! Even the Action Replay cheat doesnt work for him. It's really sad, because I want to get him too.
But, I did hear that you will be able to get him in Poke'mon Emerald...I don't know if this is true...but I sure hope it is!
1. Espeon and Umbreon can only be gotten in Ruby or Sapphire, because it measures the time of day. Espeon in the morning and afternoon, and Umbreon at night.
2. To get into the Dotted Hole, use Cut.
3. The last password is at the bottom of the Dotted Hole, where a guy steals the Sapphire from you and tells you the password.
it does work! i got the code from www.codejunkies.com, here are the codes:
2. Encounter Main Code
(all of these must be on for it to work and you may not encounter mew straight away you may encounter a random wild pokemon but kepp walking around in the grass and you will find him)
The encounter main code is bad. I've been working with it for a couple of weeks now, and it wont work on pokemon in the numbers between 1-164 and numbers 252-386. I don't know why... But I think it might be just my AR.
There is an Island 7, and Island 8 you can either get from a Gameshark/AR/CodeBreaker code, or a Nintendo endorsed even, like Poke'mon Rocks America 2004 (which has gone by! )