To unlock Parody Mode, beat the game once. You'll now have the option of turning on a joke dialogue track.

Go to any room that has breakable items like pots and stuff that spawns items when they break. Simply break the pots, exit the room, and come back in and do it again.

After you clear the game, a Bandai e-mail will tell of something called a "Mummy Ship". The extra boss is inside.