Siren of Hazy Maze Cave

The Siren of Hazy Maze Cave is a nickname given to a rare anomaly that may occur in Hazy Maze Cave. It is notable for appearing only on copies that have little to no personalization, with copies that have a high Wario Approximation seeming to have little to no chance of a Siren encounter. Interestingly, no reports of the Siren are reported on emulation or other versions of the game that lack the Personalization A.I.

Anomaly Description
The anomaly can very rarely occur while in any Mission and Area of the main course. It is characterized by a loud, siren-like alarm noise that plays at a high volume for exactly 30 seconds. During and after this, the course will be swiftly updated to include different sign text and occasionally even a Siren NPC (see below). These changes are often glitched or corrupted in nature, and appear to be generated quickly in response to the siren noise.

The Siren NPC
The Siren is an anomalous NPC known only to be associated with the Siren of Hazy Maze Cave. It appears to use edited models of other NPCs in the game, commonly Princess Peach or Toad. The NPC is described to have broken animations and simplistic textures that appear to be generated entirely by the A.I.

In most reports, the Siren can be interacted with, and usually produces simplistic dialogue that may refer to the location of a Star. It may also, however, behave as a form of enemy or mini-boss. When it behaves as an enemy, it is known to behave functionally identical to existing enemies that appear within Hazy Maze Cave, although "upscaled" in some form, most commonly requiring several hits to defeat.

Defeating the Siren usually drops a Star, most commonly whichever Star was selected in the Mission Select menu.

The Re-Boot Anomaly
In some rare instances, the game may fail to generate a Siren NPC. In this case, the Alarm will continue, before the game goes entirely black and restarts instantaneously. This often results in Save Data being lost, corrupted, or altered in various ways (lives, star counts, collectibles).

Theorizing
Earlier builds of Super Mario 64 have been reported to include a "Siren Debugging Feature", wherein the game will make a loud siren noise identical to that of the Siren, before forcefully closing the game. This appears to be a de-bugging feature that was used to test the A.I. and make sure it was working as intended, by alerting testers when the copy hasn't received adequate personalization to its intended effect.

The Siren of Hazy Maze Cave appears to be this event actualizing in the retail release, presumably triggered by the A.I. accidentally when attempting to personalize Hazy Maze Cave. It appears to "panic" in some capacity, swiftly attempting to cover its tracks by hastily making an NPC using the name "Siren", and cancelling the sub-routine of the Siren Debugging Feature. This theory explains the glitches and related corruptions that happen when the Siren is triggered; The A.I. works fast, resulting in buggy code and animation.