Instructions
Insert the "Pokemon Diamond" or "Pokemon Pearl" cart into the Action Replay, then push the Action Replay into the DS. There is a cartridge slot at the top of the DS that the Action Replay slides into. Make sure the Action Replay clicks into place.
Enter this code at the Action Replay cheats screen:
94000130 FEFF0000
B21C4D28 00000000
B0000004 00000000
DA000000 00112F58
D7000000 00024A9C
D2000000 00000000
Press "Start" to continue.
Select your "Pokemon" save file with "A" and continue your game.
Bring up the calculator app for the Poketch at the bottom of the screen. Type in any number from one to 250. Bring up the Pokedex from the options menu and hold the "L" and "R" buttons. This will change your sprite.