Pokemon Diamond Cheats :
Glitch - Surf Glitch
This only works for Diamond and Pearl, not Platinum.
Go to the Pokemon League with a Pokemon that knows Surf. Enter Aaron's room and use Surf. You can go through the walls and go to the flower place where Shaymin is found(I'm not sure what it's called...) and catch Shaymin without Oak's Letter, and you can catch Darkrai too.
This glitch was recognized by the makers and was fixed. But if you have an older copy of Diamond, you may be able to do this.
NOTE: IF YOU ARE SUCCESSFUL WITH THIS GLITCH, YOUR SAVE FILE MAY BE CORRUPTED AND YOU WILL HAVE TO START ALL OVER AGAIN.
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