Secret characters:
Go into Blast, then press Down(2), Right, Left, Right, Up, Left, Down, Right. Then, go to the character selection screen. Cosmo, Wanda, Patrick, and Carl Wheezer will now be unlocked.
Unlock the Bungi games:
Highlight the Bungi game at the bottom of the game selection screen, then press Up(2), Down(2), Left, Right.
Unlock the Clam games:
Go to Blast, then press Up(2), Down(2), Left, Right, to unlock the levels for the clam games.
