Starlight Skyrise

Not to be confused with Star Road, a supposed secret hub world with several unique levels associated with it.

Starlight Skyrise is the name given to a course found in few personalized copies. The course is decorated with several star shapes in both the geometry and the skybox, similarly to World Star from New Super Mario Bros. 2. It can appear as a small level, a full course, or even a Cap Switch level. The level can reportedly be accessed through a painting, a secret warp, or by looking upwards in a certain area similarly to Tower of the Wing Cap. The level geometry is often made up of several flat, translucent tiled planes and may sometimes feature clouds, floating ships, or similar sky-themed platforms.

The course has also appeared under the name "Star World".

Description
Starlight Skyrise is described as a blue and cyan world with several star shapes and planes scattered around it as decoration or platforms. The level geometry is almost entirely translucent, and usually changes colour. There are usually several star-shaped platforms used to navigate to higher parts of the level, however other sky-themed objects may also spawn. Notably, no enemies have consistently been reported in this level.

Starlight Skyrise has been associated with the supposed Rainbow Cap Switch, as well as the Rainbow Cap and/or Starman power-ups tied to the Rainbow Cap Switch, likely due to the level's association with stars. Most reports claim that this level is where the Rainbow Cap Switch can be found and activated when both anomalies appear in the copy. However, several other reports claim that the level simply uses the power-ups similarly to Wing Mario Over the Rainbow instead. Interestingly, the course has only ever been reported as being accessible via painting once.

Stars
Few stars have been reported in Starlight Skyrise, despite claims of the level sometimes being a full course. The 2 most common stars are obtained by collecting 8 red coins, and reaching the top of the level with the star platforms. Other stars reported are much more inconsistent and unconfirmed, but include breaking a yellow ! box somewhere in the level containing a star, somehow transforming a decorative star into a collectible one, and flying through several checkpoints marked with either Stars or Coins.

Theorizing
It is believed that Starlight Skyrise was removed from Super Mario 64 due to the Rainbow Cap Switch and Rainbow Cap and Starman power-ups being removed. Another theory suggests that the level was scrapped due to time constraints, as it appears very simple and potentially unfinished, including the name's simplistic nature. A final theory suggests that the level's theme and design clashed with the other levels and overall theme of the game, causing it to be removed and possibly replaced with another level.