Mario Decal

The Mario Decal is the name given to an anomaly present within Super Mario 64 in which an entity with the texture of Mario's jumping sprite from Super Mario Bros. is present within a stage; The entity replaces other objects present within the level, most commonly trees, causing it to appear more frequently in stages such as Bob-omb Battlefield.

Behavior
The entity stays still and can be interacted with, though the result of the interaction differs from case to case; Upon interacting with it, it will often display a random piece of text from the game before giving the player a star (known as Decal Star by the community) which crashes the game when taken, though there have been reports of it giving the player coins, 1-ups, red coins, and secrets.

There have also been reports of it taking on the attributes of the entities it replaces, such as being able to be broken by Mario when replacing a box, some have also reported it teleporting the player to other areas or stages, though this almost always results in a crash due to taking the player to a level that doesn't exist.

Trivia

 * It is theorized by the community that the entity was originally a placeholder used to test out certain mechanics, such as teleportation, text boxes, and NPCs granting stars, and that other behaviors, such as granting red coins and replacing other objects, are a result of changes made by the Personalization AI.
 * Interacting with the entity may crash, permanently glitch or even fry your game, as it may interpret code not meant to be text as text; This has led to reports of the Personalization AI malfunctioning within play.