Princess Peach's Castle/Fourth Floor

The fourth floor is a hidden floor of Princess Peach's Castle. While most copies of Super Mario 64 depict the castle with only three floors alongside a basement, some rare copies include a floor above the third. The contents of this floor vary from copy to copy, though most interpretations feature spanning hallways of nothingness with Boos roaming them aimlessly. Other players have seen Waluigi running in the halls, laughing insanely.