Fight as Baiko and Tamasaburo
Press [L1], [R1], [L2], [R2], [L1],
[R1], [L2], [R2], [L1], [R1], [L2],
[R2] at the character selection screen.
Bonus accessories
Press [R2], [L2], [R1], [L1], [R2],
[L2], [R1], [L1], [R2], [L2], [R1],
[L1] at the parts selection screen.