Textureless Mario Anomaly

The Textureless Mario Anomaly is an anomaly only known to exist in individual personalized copies. Encountering this anomaly implies future bugs and crashes. It can also occur in altered ROMs through unknown means.

While this anomaly is active, the HUD and screen will flicker. Various 3D objects, the pause screen, and other map geometry will appear to be black. When the player interacts with the objects, the game will freeze or crash. In more personalized copies, an error screen will appear instead. Water textures will also appear to be completely invisible. When this happens, the music and sound effects will not play while the anomaly is present. Mario will lose all texture, appearing to lose their face, hence the name of the anomaly.

Documentation and appearances
Footage of this anomaly occurring can be found in a video made by SwankyBox on his channel SwankyZone. SwankyBox has also made a video explaining how he discovered this anomaly. Watch his video here.

Greenio's Tapes
This anomaly appears on one of Greenio's tapes, specifically in 11.15.95, where he briefly appears in 1:20 in the room with the trapdoor to Bowser in the Dark World. The screen goes black, and then this anomaly shows up close to the camera in the black background with the message "I'M NOT HAVING FUN," then his red and blue color turn black, and the screen goes black.

Further text in the video shows the entity to take on a more benevolent manner, advising and pleading with the viewer to find their way to the Fourth Floor and to end the source of the suffering of likely itself and others.

It also appears in the videos Beta Bob-Omb Battlefield, Deeper Cavern, Genesis and Aftermath.

The AI's personalization, Stanley, is based off Textureless Mario.

Theorizing
Considering that the only available footage of this anomaly was from a ROM hack where coins replace all the objects, Nintendo's adaptive A.I. is likely trying to reprimand and punish the player for tampering with the game. It could also be an anti-piracy system.

A hidden message within the footage of the anomaly seems to imply that the anomaly and Wet-Dry World are connected.