Princess Peach's Castle/Castle Balcony

The Castle Balcony is an anomalous area found in some personalized copies of Super Mario 64, usually accessed via a doorway in the Third Floor or Second Floor of Princess Peach's Castle. It usually appears as a long half-circle balcony hanging over either the Castle Grounds or Castle Courtyard. This area has several associated levels and unique phenomena, despite the area's small size.

Geography
The Castle Balcony takes the appearance of a simplistic area made of a half-circle balcony connected to either floor it can be accessed from. It has been reported to be either entirely in the sky, or allow sight of the Castle Grounds or Castle Courtyard, anomalous replacements such as the Castle Fields, and even the Tower of the Wing Cap in one report, all of which which can be jumped down to in some copies. However, most prevent this with invisible walls. Notably, some reports state these areas are otherwise inaccessible.

Notably, there is commonly a painting above the doorway leading to the Castle Balcony. This can usually lead to a sky level, such as Rainbow Ride and Wing Mario Over the Rainbow, though can also lead to anomalous levels such as The Sun, or the Castle in the Sun level reported in the Peaceful Grounds. However, an exclusive level named the Secret Sky is the most common level reported.

Some reports state that there is a path jutting out of the walls of the castle surrounding the balcony, that when reached and followed, either a castle's secret star can be found, a broken wall allowing access to a new floor, most commonly being the 4th Floor, or a new level, usually being the same potential areas as the painting in the main part of the Castle Balcony, though a new course known as Misty City has also been reported to appear.

A final area that can reportedly be found through the Castle Balcony, a floating island in the sky known as Sky-High Isle, can be accessed by flying towards it using a Wing Cap that can be found somewhere on the balcony. The island itself sometimes does not actually appear as a level, simply being part of the Castle Balcony, though usually still functions the same as it's level incarnation.

Anomalous Klepto
The most common anomaly related to the Castle Balcony is an anomalous Klepto that usually has different colored feathers, similarly to an Enemy Discoloring. It can be holding a star, attack the player, allow the player to grab them and fly around similarly to Hoot, or they can be a large Klepto that can be rode similarly to Dorrie, with the latter two usually being used to access Sky-High Isle if a Wing Cap isn't present.

Reused Islands
According to some reports, some floating islands similarly to those from Whomp's Fortress can be found, usually either as decoration or have coins or a castle's secret star on it, or may even contain a cannon that can be used to reach Sky-High Isle. Notably, one of these islands can also reportedly be the one from Bob-omb Battlefield, potentially due to the Personalization A.I. reusing assets, though the island is notably part of the level's geometry, which the Personalization A.I cannot alter, meaning this island could instead be a recreation.

Castle Roof Replacement
In copies where this anomaly is located in, the items on the roof of the castle as well as the cannon in the Castle Grounds disappear. However, it can instead be accessed by jumping to it from the Castle Balcony if it is accessed via the Third Floor. This part of the roof usually has Yoshi, a Wing Cap and the several 1-ups, similarly to the regular roof, though it can also be the location of one of the anomalous levels associated with the Castle Balcony via a painting on the tower.

The Castle Fields
Main Article: Princess Peach's Castle/Castle Fields

The Castle Fields are an anomalous replacement of the Castle Grounds or Castle Courtyard that appear as an open valley with several hills. The area itself is usually accessed from the Castle Balcony by jumping off of the balcony, similarly to the way to commonly access the Castle Grounds or Castle Courtyard.

The Secret Sky
The Secret Sky appears as a cloudy area requiring the Wing Cap to traverse, similarly to Wing Mario Over the Rainbow, though it does not have any floating islands or rainbows. There is usually only an 8 red coins star, though others have been reported, such as finding a star by reaching the top of the level or collecting 5 secrets. The only enemy reported to be in this level is the Chuckya.

Misty City
Misty City takes the appearance of the top of a large city covered in fog. The bottom of the city can usually be seen, though a death barrier usually blocks access to it. There are usually very few notable landmarks on the roof of the buildings except for occasional fans or doors appearing to lead into the buildings. This level is potentially referenced in Super Mario Odyssey with New Donk City. The most common stars reported in this course are a 100 coin star, an 8 red coin star, and a star found by climbing to the top of a lightning rod on top of a building. The most common enemies reported in this level are Fly Guys, Chuckyas, and Goombas.

Sky-High Isle
Sky-High Isle is the third and final level that has been documented alongside the Castle Balcony, taking the appearance of a large floating island. It usually does not appear as a full course, though it has reportedly appeared as a course, though it is more commonly a smaller level. The most common stars reported are finding a star at the top of the island, collecting 8 red coins, and a 100 coin star when the level appears as a full course. This level is notable for sometimes appearing as part of the Castle Balcony with most of the stars that can be reported alongside it. The reported enemies are Goombas, Piranha Plants, Fly Guys, and Chuckyas.

Trivia

 * Seen in one of the patents for Super Mario 64, an area is listed as a balcony. However, this appears to be a separate area, as it appears to label a higher part of the First Floor of Princess Peach's Castle.
 * Found in Super Mario 64 DS' Rec Room is a window looking out onto a small balcony known as Peach's Balcony, as the window is in the area known as Peach's Room. This balcony is inaccessible, and much smaller than the Castle Balcony, though it could potentially be a reference to the anomalous area. Peach's Balcony itself is also a rumored area that could supposedly be accessed.