I Know how to catch!!!
Ok first u need fly, Ok when u go up the 5 people bridge dont!
fight the the Youngster that is standing neer the rock who has a Slowpoke ..... Ok when u get to lavender town when u go to the root to the left dont fight the Gambler (well i think it is) that has a poliwirl i think then get fly... Go to the underground tunnel from Celidon to laventer town and save out the door then save .... Then move down but press start as soon as u move down so the Gambler cant battle u. If u battle him reset and try again. Then Fly (The Gambler wil get a ! over his head like he wants to battle but your alredy gone fly to Celdon u cant go to the start menu then go up to the Youngester that u didnt fight battle him But make him MOVE!
then u can go to start menu then fly to laventer town and save then go to the root to the left and the start menu will pop up then cancel then a Level 7 Mew will appear he only has Pound...... Have about 20 grest balls cause his hard to catch after that happy mew in your hands
.... Trust me Ive dun this cheat 3 times it works and his better then Mewtwo!
Cheers hope i help u