Where do you find a Mewtwo in Pokemon platinum?

Answer 1

In order for you get Mewtwo in Pokémon Diamond you have to migrate it from either Pokémon Ruby, Sapphire, FireRed, LeafGreen or Emerald. If you have a friend that has one of those games and he/she has only one Mewtwo then you could tell your friend to put Mewtwo in an empty PC Box. Save the game and when it says don't turn off power, turn it off and on again. There will be 2 Mewtwoss exactly the same, same moves, levels etc. Your friend now has 100 Mewtwoss! Put the Gameboy game (Ruby, Sapphire, FireRed, LeafGreen or Emerald) in your DS and migrate. Transfer Mewtwo from the games via Pal Park (Route 221). Mewtwo will be wandering around in grass areas inside the Pal Park.