Small fighters:
Select versus mode and choose two fighters. Hold B + C on controllers one and two during the "Now Loading" screen prior to the start of the match.

Speedup mode:
Hold Start and choose a fighter at the character selection screen.

Expert mode:
Press Back, Forward, Back, Forward, then Forward, Back, Forward, Back at the "How to Play" screen.

Hint: Super Super Death move:
To perform the Super Super Death Move (Cho Cho Hissatsuwaza), hold A + B + C + D and repeatedly tap Start at the start of the fight but before "Go" appears. Your character's name will turn green to confirm correct code entry.