Vampire Chronicle

Go to the character selection screen and highlight the "?",
and press the following button combination:

Unlock Shadow as playable character: Press Start(5 times) and A, B, X, or Y
Unlock Marionette as playable character: Press Start(7 times) and A, B, X, or Y

Change the background colors
While select a background hold Start and push A, B, X, or Y

Unlock EX menu
Highlight the "Options" at the main menu, after hold R + L
and push A on a controller. Push Z + C on an arcade stick.

Unlock Oboro Bishamon as playable character:
Go to the character selection screen, highlight Bishamon,
then hold Start and press A, B, X, or Y.