Super Mario 64/July 29th 1995 build

The July 29th, 1995 build of Super Mario 64 also known as the 1995/07/29 build, is an anomalous and mysterious build of the game. It dates back to before the Ultra 64 (the initial name for the Nintendo 64) was even patented, making it perhaps the oldest piece of Nintendo 64 history so far.

Because of the sensitive nature of the build's contents, research on the 1995/07/29 build of Super Mario 64 is highly discouraged. It is on the infamous iceberg discussing Super Mario 64's anomalies.

Speculation
It's likely the 1995/07/29 build wasn't even related to Mario at all or created by Nintendo. Instead, it was created by an unknown Japanese organization that produced the technology responsible for Super Mario 64's ability to personalize itself to its player's likeness. This build would then be sold to Nintendo and reworked into Super Mario 64.

This build allegedly has an intense texture bug which causes the textures to change colors rapidly and induce seizures within playtesters. It's rumored these playtesters would go on to experience horrific and nightmarish hallucinations, which seem to be the origins of some of Super Mario 64's most horrific anomalies.

Reportings

 * Everything in this section should be taken with a grain of salt. These are all unverified claims.

Developer Anecdote
An anonymous user wrote of their experience talking to a foreign friend from Japan back in 1995. Their friend used to work at Nintendo, and he remarks of his time working there and working on the very first build of Super Mario 64.

The former programmer and his team was handed the prototype after Nintendo bought it from another Japanese company. The team were tasked with cleaning up the prototype for the Ultra 64. The programmer explains how this build bore no resemblence to the happy-go-lucky Mario franchise, and instead was a rather desolate build. He doesn't recall the appearance of the player character, but refers to them as looking rather "simplistic, like a low-poly ordinary man".

He goes onto discuss the castle itself. Unlike the retail release, the castle was made into one full map meaning that all the castle was smaller to fit into the exterior of the castle. Remnants of this are actually seen within the demos of the game seen within game shows, where the rooms with a painting are alot smaller than they are in the release of the game.

The programmer goes into great detail of the basement. The basement was alot darker in this build, and had rather advanced fog for Nintendo 64 standards. According to the programmer, the basement acted as a testing ground for an experimental artifical intelligence that would track the player's "cognitive desires" and subvert them within the game. With this, the basement would usually span endlessly like a labyrinth. One playtester, who the team neglected to check on before leaving the office for the night, was found still playing the game in a delirious and crazed state. He was taken to the hospital shortly after being found, and later playtesters were urged not to enter the basement.

When asked about the upper floors, the programmer said that there wasn't much interesting up there; it was a boring and thin spiral staircase that led up to what seems to be a bedroom. He was surprised to hear about a supposed fourth floor and says that "considering Nintendo made the castle bigger with the use of sub-areas, it wouldn't be surprising that they would try to add yet another floor."