Originally posted by TheScythe at GameFAQs Message Boards
If you don't believe me, try it yourself.
I predict about 99% of the replys to this post will be people who won't even try this, and will just poo-poo it the second they see it. If you bother even TRYING this code, you might actually see that this works. And, please, if your going to start and hate me, only hate me if the code didn't work for you. It should work. No mindless babbling about how I'm a liar. Because I'm not. About this anyway.
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-Make sure you haven't battled the Youngster with a Level 17 Slowpoke, on the way to Bill's house. If you have, the code won't work.
-Also make sure you haven't battled the Gambler with two Poliwags and a Poliwhirl. He is facing the Underground Path toward Celadon city...on Route 8. If you have, the code won't work either.
-You need Fly. (Aka HM02)
-Get some Ultra Balls, and anything else you would use to catch a Level 7 Mew, that only knows Pound.
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Go to the Gambler I talked about before. Save AT the door he is facing. Don't make him battle you. SAVE HERE, this is tricky. Now, step one step towards him, and PRESS START. Really fast. If you did it right, it will pop up, but he won't battle you. (This shouldn't work for any other trainer) Now Fly to Cerulean City.
[If you've done this right, after you use Fly, he will get the "!" over his head]
Note: You cannot use START, A, or B.
Note: Do NOT save anywhere after this. First of all, you can't save when your buttons don't work. But second, when they work again, saving will ruin the Mew code, and not allow you to get the Mew. Ever. Keep your saved file from before you battled the Gambler.
[If you've done this right, you can't press Start]
Walk (you can't use start) to the Youngster, and when you battle him, make sure he WALKS TO YOU. Don't go directly in front of him. Beat him, and (now your buttons work) Fly to Lavender Town (Or Saffron City).
[If you've done this right, the Start menu WILL pop up when it should]
Now if you went to Lavender, go to the left of town, and start to enter that narrow passageway. If you went to Saffron, go right, to where the guard lets you past if you give him a drink. Either way, the Start menu will pop up. Do NOT save here. Press B. Mew will appear. This is your ONLY chance. (unless you go to your save file before the Gambler) Ta-Da...its a Mew.