At the Options screen, quickly press Y, X, B, A, L, R. The screen flashes red to confirm the blood code. Don't expect to see buckets of red, though.
On story mode (after defeating Voodoo), instead of going on to fight Beast, go back to "The Lost Jungle" and hit Start. This will take you to a bonus stage.
Character Select for Story Mode
At the option screen press these buttons very quickly; Up, Down, B, Left, Right, B. Now you can play as another character.
Fight Beast in Story Mode
On the first island, go to the lower right-hand corner, walk down the stairs and press Start to fight Beast. Submitted by Melvin Banks
At the options screen press these buttons very quickly; Up, Right, B, Down, Left, B. Go to DUEL MODE and when you start the game, during the level press X + B at the same time. The background will disappear.