How to Get Mew in Pokemon Red, Blue and Yellow?
Over the years there have been many convoluted and absurd “techniques” to legitimately obtain Mew, “Mewthree,” or other “Pokegods” in Pokemon Red, Blue and Yellow without the use of cheating devices or real world events. Most of those were complete fakes and beyond wastes of time. However, there is one technique that works, that is easy to do, and can be done early in the game.
To do this trick, it is imperative that you have not battled the Bug Catcher Trainer to the left of Nugget Bridge in Cerulean city or the Swimmer Trainer in Misty’s gym (or Misty, for the matter, since beating the gym leader prevents you from facing the gym followers). You must also own a Pokemon that knows “Teleport,” the easiest to obtain being Abra, which can be found on Route 24 and 25, above Cerulean City in Red and Blue, and on Route 5, 6, 7 and 8 in Pokemon Yellow.
Once you have Abra, make sure you stop in the Cerulean City Pokecenter, since we’ll be using teleport and we want to return to Cerulean City. Make sure you have Abra in your party and defeat Nugget Bridge like normal. Walk to the left of the bridge and you’ll see a path heading south. Before you head down, be sure to save. When you head down, a bug catcher trainer appear at the bottom of the screen and spot you. Immediately before the (!) sign appears above his head, press start and have Abra use teleport. If you fail to do it the first time, reset and try again.
Once you have aborted the battle and teleported back to the Cerulean City Pokecenter, you’ll notice that you cannot access the start menu or talk to NPCs. This is because the game has been tricked into thinking that you’re still in a fight. Next, you need to enter the Misty’s Gym and fight the first Trainer, the Swimmer, whose final Pokemon is a Shellder with a Special stat of 21. Next you will need to proceed back to the Nugget Bridge. As soon as you set a foot back inside Route 24, the game will freak out and think that you’re supposed to be in a battle, so it will throw you into a random encounter. What you run into is based on the Special stat of the previous Pokemon you battled, which ought to be 21, which corresponds to Mew. If you’ve done everything right, you ought to run into a level 7 Mew.