Enter these codes at the title screen:

* Yami Yugi: R, LEFT, B, RIGHT, Up and R, RIGHT, DOWN, A
* Kaibaman: DOWN, B, LEFT, RIGHT, RIGHT, R, Up and R, A
* Yami Bakura: L, DOWN, RIGHT, LEFT and B, R, DOWN, DOWN, A
* Grandpa: L, RIGHT and B, RIGHT, B, R, LEFT, DOWN, A