The Sun

Sky Seas is an anomalous level found in some personalized copies of Super Mario 64. Similarly to The Starry-Night Skies, the level is most commonly associated with a painting of the sun and clouds that is normally unable to be entered in standard copies. However, several reports claim that the painting is indeed accessible, and most commonly leads to a level named Sky Seas, often compared to Rainbow Ride and Wing Mario Over the Rainbow.

Description
Sky Seas is often described as a large area with several clouds, usually traversed with the Wing Cap or occasionally even Hoot, as well as several floating islands and reused assets from Rainbow Ride, causing some to believe this level is created through Dynamic Level Arrangement or was the original version of Rainbow Ride before being scrapped.

An area above the main part of Sky Seas taking place in space has been reported, even having a new skybox, making this level the only level documented with changing skyboxes excluding changes by the Internal Clock. This area, instead of having clouds, would have meteors and asteroids used to traverse the level, and even supposedly would have explorable planets and alien versions of enemies, though that is unconfirmed.

Another commonly reported section of Sky Seas is an area where a portion of the clouds are storm clouds, supposedly with a unique rain effect most commonly reported in Raging Rain World as well as a unique lightning hazard that randomly spawns and damages the player upon contact. A minor amount of reports state that this area moves throughout the level or can disappear entirely, or is somehow tied to the Internal Clock anomaly or something similar within the copy being able to detect weather in the vicinity of the player.

The most common enemies reported in Sky Seas are Fly Guys, Fwooshes and Lakitus, though other enemies such as Goombas and Whomps have been reported to appear on the clouds. Notably, several ground-based enemies have been reported to appear with wings, mimicking the para-enemies seen in other games throughout the Super Mario Bros. series.

Power Stars
The 3 most common Power Stars in Sky Seas are reportedly obtained by accessing a certain area, collecting 8 red coins, and collecting 5 secrets, usually in a specific area. Some other, more uncommonly reported Power Stars, can supposedly be obtained by managing to get rid of the stormy area of the level, defeating all the enemies in a certain area, or fighting a winged version of a boss such as a Wiggler or Big Bob-omb. Some have even reported a unique boss fight against a large bird, though these reports are heavily debated.