Level and room select:
Enter HOUSE as a password and begin game play. Press R1 during game play to select a new level or R2 to choose a room. Alternatively, hold L1 and press Select during game play to choose a level or R2 to choose a room.

Invisibility:
Enable the "Level and room select" code, then advance to the ending sequence. Wait until the credits complete, then advance through the level names two times until you get to the house. When you reach the house, you will be invisible.