Instructions
Turn on your Pokemon game with a cheat client running.
Enable the "Steal Pokemon" cheat and the "100% Catch Rate" cheat.
Travel to Sunnyshore City, then head north across Route 223 until you reach the Pokemon League. If you are having trouble finding Sunnyshore City, consult the world map.
Save your game before entering the Pokemon League. Bad eggs will not always occur, so you may have to repeat the process several times.
Speak to a member of the Elite Four to initiate combat. When a member of the Elite Four summons a Pokemon, throw out a Pokeball to catch it. You will receive a message stating that the trainer's Pokemon was caught.
Open your inventory and confirm you have received a bad egg. If you did not receive a bad egg, restart the game and attempt the procedure again.