The Statue Lurker

The Statue Lurker is an anomalous entity found in some personalized copies of Super Mario 64. It reportedly appears in the Castle Courtyard and Inside the Fountain. It is usually either described as a long thin quadruped entity with black skin, claws on it's hand and feet, white glowing eyes and a malicious smile or a tall zombie-like Luigi missing their lower jaw with a star on their hat and impaled with a piece of the Eternal Star Statue, the latter of which also being nicknamed the Courtyard Crawler. It is highly violent and similar to the Wario Apparition in viciousness.

Description
As already stated, the Statue Lurker has 2 forms: The "pure" form, and the Courtyard Crawler. The former of which appears more commonly Inside the Fountain while the Courtyard Crawler typically appears in the titular Courtyard, though sightings either way have happened. If they appear in the Courtyard, there is reportedly a cutscene where the Eternal Star Statue will slide open, revealing an opening for the monster to come out. Upon sighting the player, they will instantly rush towards them while the area they are in will extend in size, typically creating an endless hallway, similar to that of the Wario Apparition's encounter. If the player is caught by them, the game will reportedly crash or the player will lose all of their lives and appear on the game over screen similarly to Mother Dorrie, sometimes even losing entire save files. However, if the player does escape and it appeared in the Courtyard, it can reportedly unlock Inside the Fountain.

Notably, the pure form typically only screeches and hisses at the player though the Courtyard Crawler more commonly speaks in a scary, deep voice, most often saying "IT'S ME... BROTHER...," referring to Mario. It is worth noting that if the Courtyard Crawler is encountered, some have reported that Luigi will not appear in any capacity, likely due to the Courtyard Crawler appearing to be an undead Luigi. This has led some to infer that the Courtyard Crawler is a dead version of Luigi, or even the Statue Lurker's pure form disguised as Luigi after killing them, though this is unconfirmed.