I got this from a mag so some might know it.
[SIZE=3]Pokemon and Item Cloning[/SIZE]
First go to a PC in a Pokemon Center, stand in front of it and save. Then start the PC, go to Bill's PC, and deposit the Pokemon and Item (it must be hloding it) into a box (example: Lugia holding a Master Ball) then go to change box and choose an EMPTY box. Say that you will save and as soon as the word SAVING appears turn off your Game Boy. Turn it back on and the Pokemon that you chose is still in your party and it's in the box!! You can clone 5 Pokemon and Items at one time using this code.
And if you're trading and it messes up, a Pokemon might be cloned. It happened to me once but I don't know how.
:)