Clay Fighter 63 1/3 

Secret options mode 
At the character selection screen:
hold L and press C-Up, C-Right, C-Left, C-Down, B, A(2).
If you entered the code correctly, the screen will flash.
Press B to exit, then enter the options menu.
Choose the "Secret Options" selection to access different body sizes,
voices, backgrounds, camera flights, claytality timer settings,
and camera control using controller four.

Play as Sumo Santa 
At the character selection screen:
hold L and press A, C-Down, C-Right, C-Up, C-Left, B.

Play as Dr. Kiln 
At the character selection screen:
hold L and press B, C-Left, C-Up, C-Right, C-Down, A.

Play as Boogerman 
At the character selection screen:
hold L and press Up, Right, Down, Left, Right, Left.

CPU control 
At the character selection screen:
hold L and press A(5), C-Up, C-Down, C-Left, C-Left, B, A, C-Right.

Programmer's mode 
At the character selection screen:
hold L and press A, B, A, B, A, B, C-Left, C-Right, C-Up, C-Right, C-Left, C-Right.
This mode allows any character to be selected, and has an overhead view of each stage.

Random fighter select 
At the character selection screen:
hold L + R.

Alternate costume colors 
At the character selection screen:
press A for color scheme one or C-Down for color scheme two, then press B to exit.

Same costume colors 
At the character selection screen:
press C-Up on either controller to select any fighter.
Then, have the other player highlight the same character and allow the timer to reach zero.
Both fighters will now be the same color during the match.

Stage select 
Select two player mode:
then press C-Left or C-Right at the screen that displays the current stage.