You must have the following requirements DONE!!!
Unlock Sound Test (Have every stage, character, and all 51 events BEATEN)
Beat Event 29, a total of 50 times
Beat Event 1, a total of 700 times
Beat Event 48, a total of 65 times
Beat Event 43, a total of 100 times
Beat Event 23, a total of 1000 times!!!
Beat all of the other events (except the ones that I meantioned) a total of 75 times!!!
YES, its long work, but it pays of because you can used ANY Yu-Gi-Oh Card in the whole world on Super Smash Bros. Melee!!!
AND...
If you get an Action Replay when you have this stuff unlocked, type this code, you'll will be able to create a WHOLE NEW YUGIOH GAME ON YOUR SUPER SMASH BROS. MELEE DISK (you will still have your normal Super Smash Bros. Melee Game on it) its called Yu-Gi-Oh: The Next Millennum

9E9945BA 23CA6BB3
D145AC68 B09DD237

And there you go.