Nostalgia Dream Anomaly

The Nostalgia Dream Anomaly is an event that refers to the appearance of rare specific locations within the game of Super Mario 64 that bare ressemblance to locations of certain dreams. The most common case results in a large map spanning a large courtyard with multiple huge buildings that bare a ressemblance to Peach's castle. These areas are commonly found in demo versions of Super Mario 64 and commonly have a time limit attached to them, making them hard to navigate with limited time of exploration.

Sunset Field
Sunset Field is a seemingly infinite field with hills in the background that has randomly generating objects. In early prototype game files, there is a single image reminiscent of this area. Not much else is known about the are other than the link to several prototype builds that have a pink sunset.

Tree of Peace
Tree of Peace (Formely known as The Tree of Peace and Calm) is a room found within the 4th floor when the anomaly occurs. This room supposedly has nothing important in it other than a huge tree and a single unkown course. This room is also said to automatically regenerate Mario's Health. The Tree itself is known to have a treehouse inside of it with mutliple beanbag cushions, however there are no screenshots or proof that said room actually exists other than another square image the same resolution as the Sunset Field one.

Castle of Education
The most commonly described location, known as the Castle of Education, is a large area that bares ressemblance to Peach's castle and a school. It contains a main building with a hall looping itself in a rectangle, along with a set of smaller buildings near it and multiple segments of a building in the shape of a wall, with a tail sticking out.

Causes
The exact causes of this anomaly are unkown, however it is said to be linked to The Starry-Night Skies, as completing the level could generate these spaces. Another theory suggests that it is caused by having dreams and that the stages will present locations of your dreams after you've had them.

Trivia

 * Shared Nightmares can theoretically be connected to this, considering both involve dreams connecting to the game shared by multiple people.
 * The Wing Cap is automatically enabled in the Tree of Peace
 * Other stages, such as Tall, Tall Mountain and Tiny-Huge Island may be effected and change appearance.