Eternal Star

The Eternal Star, sometimes referred to as the 121st star, is a rumored collectible in Super Mario 64. It is believed to exist from the engraving on the Castle Courtyard statue's plaque, which some have interpreted as "Eternal Star". It is often described as a large star. Some people say the Eternal Star is actually the star dropped by Bowser at the end of Bowser in the Sky.

How To Obtain
There are several rumors about how to obtain the Eternal Star. These include:


 * Simply beating Bowser in the Sky, as the big star at the end is the Eternal Star.
 * Running around the Eternal Star Statue several times.
 * Finding a hidden level and completing it, most commonly a Bowser level.
 * Collecting all 120 stars and finding it somewhere, often the Castle Courtyard in place of the statue.

What It Unlocks
Those who have documented to collect the Eternal Star have said it has unlocked several different things. These include:


 * The 4th Floor.
 * A new ending.
 * A hidden level, most commonly a Bowser level.
 * Appearing on the save file as an achievement.
 * Functioning as a 121st star.
 * Nothing.
 * a playable Luigi.

Theorizing
It is possible that the Eternal Star was designed to be a final collectible in the game, unlocking the/an ending, or perhaps Luigi, though was scrapped due to time constraints or some other reason. However, this conflicts with the idea the Eternal Star is the star seen at the end of Bowser in the Sky. Whether or not the Eternal Star is the 121st star or instead a separate collectible is unclear, though has been noted to function as a 121st star in some personalized copies containing the Eternal Star as a separate collectible from the star seen at the end of Bowser in the Sky.