Use the following codes at pause screen to get the corresponding result:
Baby Toy of Death: Left, Left, Right, Right, Circle Square, Square, Circle, Up, Down.
Swordfish Weapon: Up, Down, Up, Down, Left, Right, Left, Right, Circle, Square, Circle, Square.
Secret King Sword Weapon: Up, Down, Up, Down, Left, Right, Left, Right, Circle, Square, Circle, Square.
Secret Chainsaw Weapon: Up, Down, Up, Down, Left, Right, Left, Right, Circle, Square, Circle, Square.
Alternate End Boss: get all life upgrades to fight the Dark Prince instead of Vizier in the final battle.