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1) Make sure you have a Pokémon that knows Fly. On Route 8, stand in front of the door of the Underground Path. Save your game, since saving after this point will disrupt the procedure. 2) Walk down one step and immediately press Start. If you succeed, the menu will pop up before the Gambler "sees" you. Go to the Pokémon list and fly to Cerulean City. The Gambler will see you just before you fly away. 3) Your Start button will no longer function. Go north across Nugget Bridge and head east until you find the trainer in this picture. http://www.princeton.edu/~jdonald/pokemon/mewglitch_files/catchmew4.gif 4) f you walk right up to the Youngster, the game will lock up, so you'll have to let him see you and walk up to you. Defeat his Slowpoke (afterwards, your Start button will work again), then fly to Lavender Town. 5) Head west into Route 8. As soon as you enter the narrow path, the menu will pop up by itself. Press B to exit......and look who it is! Mew will be at Level 7 and its only attack will be Pound. Once you've caught Mew, you can save your game without any ill-effects. How this is possable --- When you use Fly to get away from the Gambler, the game somehow "remembers" that a battle is supposed to be taking place on Route 8. This is what causes your Start button to stop working. The rest of the trick hinges on a twelve-byte section of memory, starting at memory location CD22 in Yellow (CD23 in Red/Blue), which contains the stats of the last Pokémon you fought. After you battle the Youngster, it will have these hexadecimal values: 8E 11 00 3C 00 1E 00 1D 00 1C 00 15 The first byte (8E) seems to be the same for all battles. The second byte (11) is the enemy's level (17 in decimal). The next ten bytes are the enemy's stats (HP/Attack/Defense/Speed/Special). Each stat takes up two bytes. Additionally, this section of memory is surrounded by eight bytes on each side, which all have the value 07. The last byte (15) in Yellow memory location CD2D (CD2E in Red/Blue) is the important one. It is the "least significant byte" of the enemy Pokémon's Special stat; in this case, it means that the enemy has a Special of 21 in standard decimal notation. When you return to Route 8, the game tries to resume the battle that was interrupted before. For reasons unknown, it borrows byte CD2D to use as the species identifier for the enemy Pokémon, and the next byte to use as its level. If the last battle you fought was with the Youngster, these bytes will be 15 and 07. Since Mew's hexadecimal identifier is 15, you will fight a Level 7 Mew. I used a save state made JUST for this. You can download it here http://www.princeton.edu/~jdonald/pokemon/mewglitch_files/catchmew.zip