To play as Boogerman:

At the Character Select screen hold the L button and on the D-pad press Up, Right, Down, Left, Right, Left.

To play as Dr. Kiln:

At the Character Select screen hold the L button and press B, C-Left, C-Up, C-Right, C-Down, A.

To play as Sumo Santa:

At the Character Select screen, hold L and press A, C-Down, C-Right, C-Up, C-Left, B.

To play as the Energizer Bunny:

On a one player game, pick bad Mr. Frosty and before the level begins press A, B, A, B, B, B, A, Z, B, A, Z, Z, A, C-Left. Bad Mr. Frosty will explode and you will be the Energizer Bunny!

Random Select:

Press R and L simultaneously at the Character Select screen for random fighter selection.

Stage Select:

When the Versus screen appears in 2-player mode, press any C-button to select a stage.

Change Colors:

Press C-Down - the character that is highlighted will be a different color.

Secret Options:

At the Character Select screen, hold L and press C-Up, C-Right, C-Left, C-Down, B, A, A. The screen will flash to confirm the code. Now press the B button to go back to the Title screen. Select Options, and check out the Secret Options.