Hidden options:
Quickly press Left, Left, Right, Right, Left, Left, Right, Right at the jungle title screen before the game logo is displayed. A cheat option will now appear on the main menu.

Alternate character colors:
Press B; A + B; C + B; or Option + B at the character selection screen.

Hint: Diablo's Pulverizer move:
Hold 1 + 2 then press Up, Down.