1) Deposit the pokemon you want to duplicate into a box on your PC.
2) Now switch to an empty box on your PC.
3) Turn off the game while it says "SAVING...DO NOT TURN OFF THE POWER". Wait three seconds after agreeing to save your game and overwriting the progress and all that. So the moment that the window for "SAVING..." comes up, wait three seconds. Then turn the game back on and look into your party. It should have the pokemon you deposited.
4) Check your PC, and you should find the pokemon you deposited in there as well.
Another possibility is that there are two of the same Pokémon in your box.
NOTES:
You can duplicate more than one pokemon at a time.
To duplicate items have a pokemon holding that item.
This can damage your pc, and cause you to lose Pokemon.
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