Three memory cards are required for this trick. One can be a PlayStation2 memory card if needed. Refer to the memory cards as A, B, and C. Insert memory cards A and C. Memory card A should have the cards you want to duplicate. Copy the Yu-Gi-Oh Forbidden Memories saved game file to memory card C. Start a game and insert memory card B. This memory card be should also have a game in it with a different I.D. Trade the cards that you want from memory card A to memory card B, then reset the game. Return to the PlayStation memory manager and copy the saved game file from memory card C and put it back in memory card A. Memory card A should now have your old file with all the cards that you traded to memory card B. Next, go to trade and put all the cards you traded to memory card B into memory card A. If done correctly, you should have doubled the cards that you wanted.

The following trick gives you extra cards for free without dueling or using starchips. You need two memory cards. Refer to the memory cards as A and B. Memory card A must have a save file on it. Insert memory card B into memory card slot one and start a new game. Save that game to memory card B, then reset the game. Go to the build deck menu and take all the cards you want out of your deck and exit the menu. Save your game and reset the PlayStation. Insert memory card A into memory card slot two. Go into the trade menu and select all the cards (or as many as you can) from memory card B and press Square on controllers one and two. A menu will appear. Press X to select "Trade", then "Yes". You will now have all the cards from memory card B (that you traded) in memory card A.