Shy Guys

Shy Guys are a common enemy found across 3D Mario games, first appearing in Super Mario Bros. 2. They are a race of robed creatures that wear masks, keeping their true faces unknown. They have many variants with unique colors, masks, and weapons. The most distinct variant is the Snifit, who wear dark gray masks with a nozzle mouth that shoots bullets.

Super Mario 64 Manifestation
Despite not being in standard copies of Super Mario 64, according to some reports, Shy Guys are able to appear in the level Hazy Maze Cave as hostile enemies or helpful NPCs. In the case of enemies, they replace the Scuttlebugs, found wandering around the mine and running towards the player when they approach. Unlike the Scuttlebugs, they may sometimes trip and fall onto their face while chasing Mario, leaving them vulnerable until they get back up. They can easily be taken out by jumping on their head or punching them. In the case of NPCs, they replace the signs found throughout the level, found standing where the signs would be. However, their dialogue is mostly unchanged from the normal text on the signs. They reportedly don't move and have no animations, standing static like the signs they replace.

Theorizing
It is theorized that the Shy Guys were the original inhabitants of Hazy Maze Cave, as supported by several details. Throughout the level, signs and maps are placed, indicating that groups of people once worked in this cave. The work elevator and support structures along some of the walls seem to imply that this area was once a mine. In the toxic maze, Snufits can be found hovering around, shooting at Mario if he gets close. Snufits are ghostly versions of the Snifits, which are in turn a variant of Shy Guy. One can assume that the Snufits are the ghosts of the Shy Guys and Snifits who perished in the conditions of the mine, whether it be falling into the Black Hole, getting crushed by the rolling rocks, or suffocating inside the hazy maze. In Mario Kart 8, a track titled Shy Guy Falls appears, depicting the Shy Guys working on a mining operation inside a mountain. It can be assumed that Hazy Maze Cave was one of their previous mining endeavors that ended in tragedy.

Trivia

 * The model of the Shy Guys appears to be repurposed from the Fly Guys present in the game. Their propeller has been removed, but no walking animations exist, meaning they appear to slide around on the ground. It can be theorized that this is a result of the Personalization AI reusing and repurposing existing assets.
 * A sign in Hazy Maze Cave reads "A gentle sea dragon lives here. Pound his back to make him lower his head. Don't become it's lunch." While this sign obviously refers to Dorrie, players have questioned its significance for years, considering that it is impossible for Dorrie to attack the player. It's possible that this sign wasn't meant for Mario, but instead the Shy Guys working near the lake, warning them to avoid getting close to Dorrie in case he turned aggressive. It could also be possible that Dorrie was trained by the Shy Guys to be used for transportation.
 * Despite the many colors of Shy Guys present throughout the series, only red Shy Guys can appear.