Pokémon Red and Blue/Mew glitch

It is possible to obtain the rarest Pokémon in Red/Blue/Yellow,, without using a cheating device. Players have learned how to exploit a bug in the program that allows you to encounter any Pokémon that you would like, and you can use this method to obtain a Mew for youself. It's not too difficult, but it's a good idea to save before you try this so that you can start over in case you make a mistake.

There are two primary ways to activate this glitch. No matter which method you choose, you must not defeat the Youngster with the Level 17 Slowpoke on Route #25 (marked #4 on the Route #25 map).

Method 1
The first method is at the earliest point in the game during which this glitch can be performed.
 * 1) Fight your way through all of the challengers on Nugget Bridge.
 * 2) Catch an  any way that you can, but never engage the Jr. Trainer who hides in the grass on the right of Route #24.
 * 3) Place Abra in your party if it's not already.
 * 4) Make your way towards that Jr. Trainer, marked #7 on the map.  He's the one that says "I saw your feet from the grass" when he challenges you.
 * 5) * Save the game at this point.
 * 6) Stand in front of the Jr. Trainer, just outside of his sight.  Move down until he sees you.  As soon as he does, immediately press.
 * 7) Select your Abra and use Teleport.  If you did it correctly, the trainer should have an exclamation point above his head as you Teleport.
 * 8) For the time being, your menu will not work.  This is normal.  Proceed to Route #25.
 * 9) Approach the Youngster (#4) on Route #25, but do not battle or talk to anyone else.
 * 10) You must engage the Youngster in battle from far away.  Do not walk towards him and talk to him or the game will freeze.
 * 11) Battle the Youngster and defeat his Slowpoke.
 * 12) Now walk back to Route #24.  As soon as you reach the route, your Start menu will automatically appear.
 * 13) Press  to cancel the menu, and you will instantly be taken to a battle with a level 7 Mew.
 * 14) Weaken the Mew enough to catch it, and it's yours.

Method 2
The second method can only be done later in the game because it requires that you obtain HM 02 which contains Fly, from Route #16.
 * 1) Fight your way through all of the challengers on Nugget Bridge.  You must be able to approach the Youngster on Route #25 without interruption.
 * 2) Go to the Underground Tunnel entrance to the east of Saffron City.  Make sure that you have a Pokémon with the Fly ability.
 * 3) * Save the game at this point.
 * 4) Approach the Gambler (#8 on the map) from the north.  Stand in front of him, just outside of his sight.
 * 5) Move down until the Gambler sees you.  As soon as he does, immediately press.
 * 6) Select the Pokémon who knows Fly and head to Cerulean City.  If you did it correctly, the trainer should have an exclamation point above his head as you Teleport.
 * 7) For the time being, your menu will not work.  This is normal.  Proceed to Route #25.
 * 8) Approach the Youngster (#4) on Route #25, but do not battle or talk to anyone else.
 * 9) You must engage the Youngster in battle from far away.  Do not walk towards him and talk to him or the game will freeze.
 * 10) Battle the Youngster and defeat his Slowpoke.
 * 11) Now fly to Lavender Town.  Head west back to Route #8.  As soon as you reach the route, your Start menu will automatically appear.
 * 12) Press  to cancel the menu, and you will instantly be taken to a battle with a level 7 Mew.
 * 13) Weaken the Mew enough to catch it, and it's yours.