Play as Butch
Butch (Tiny's alter ego): Hold L and press X, R, A, X, R, R on the Game Select screen.

Play as Ice
Ice: (Frosty's alter ego): Hold B and press Up, L, L, L, Right on the Game Select screen.

Play as Jack
Jack: (Octo's alter ego): Hold Up and press X, A, R, R, Y, A on the Game Select screen.

Play as Spike
Spike: (Googoo's alter ego): Hold R and press X, B, B, A, Y, Left, A on the Game Select screen.

Play as Thunder
Thunder: (Kangoo's alter ego): Hold Up and Left and press Y, B, X, B, B, X, A.

Random Select
On the Character Select screen, simultaneously press the L and R Buttons.

Speed
METHOD 1: Start a Tournament game with one player (single elimination). Play the first round. During the second round (when the two CPU players are fighting) press Reset on the Control Deck. Now go to options and you will see the speed set at 10.

METHOD 2: Go to the "Game Start" screen. Hold Y, then press L, L, R, Down, Left and R. You should hear a tone if done correctly. Now go to the Options screen and you'll be able to set the speed up to 10.

Play as Peelgood
Peelgood (Nana's alter ego): Hold Down and Left and press B, Y, Y, A, Y on the Game Select screen.

Play as Sarge
Sarge: (Hoppy's alter ego): Hold X and press L, L, Up, Down, Left, Down on the Game Select screen.

Play as Slyck
Slyck: (Blob's alter ego): Hold Y and press L, L, Up, L, Left, R on the Game Select screen.