Every copy of Super Mario 64 is personalized. Nintendo's experimental AI adapts and subtly creates a slightly altered version of the game tailored specifically for you, appealing to you subconsciously in ways you don't even notice, as well as attempting to mess with you and study how you react to it.
Have you ever played someone else's copy of Mario 64? Have you ever felt like something was just a little bit off? That's why. That's how.
This is much more than just simple experimentation with procedural generation, however. There are many layers to this, and some of them are more sinister and malicious than others.
Super Mario 64 is, at its core, an insidious and evil work of human creation.
Now, the Wario apparation (as seen here.)
The Wario Apparition was created from the subconscious wishes to see him in Mario 64 that the shared desired caused him to appear as a horrifying half start in some copies of the game. That image is what its supposed to look like, but those who encountered it ingame can't even describe what it looked like as many suffer from memory loss and stroke-like symptoms. If you suspect you're seeing it ingame its suggested you shut the console off immediately because once you give it power by witnessing it, it gains power to begin manifesting itself in your reality.