Alternate Character Color:
While selecting a character press L1 + Circle. 

Sound Test:
At the title screen hold Start and press L1 + L2 + Select + Down . 

Fight as Animal:
Select single player mode. Then, highlight Stan The Man at the character selection screen, hold
L1, and press Start. 

Fight as Master Ishi:
Complete the game in single player mode using one character.

Hyperspeed Fighting:
Hold Circle during a CPU vs. CPU match in tournament mode.