Blargg

Blargg is an enemy in the Mario series that made its debut and only major appearance in the game Super Mario World. Blarggs are red, dinosaur-like creatures that appear in lava-filled caverns, that will try and lunge out and attack the player.

Having only appeared in one game, Blargg fell into irrelevancy and would not appear in a later game. However, they were slated to reappear in Super Mario 64, and what remains of them can be found within the game's files.

Depiction
In the game's files, an unfinished and untextured model of Blargg can be found with very little functionality and a simple animation. It has a red head and body with grey teeth. The coding of the game shows that it was supposed to appear in three levels of Super Mario 64: Lethal Lava Land, Bowser in the Fire Sea, and oddly enough, Wing Mario Over the Rainbow.

The behavior of Blargg is reported to be similar to how it behaved in Super Mario World: it will start out sitting in the lava, then rise out of it. After the rising, Blargg would move towards Mario's location. If Mario is in contact with Blargg, he will be burned the same way as when he touches lava.

It is unknown why Blargg hasn't been finished for the game. One possible theory would be like how many features of games went unused or unfinished; due to time constraints.

Boss Blargg
Boss Blargg refers to a bigger version of the unused Blargg enemy that can be found in Lethal Lava Land in more transformed copies of the game. It replaces Big Bully as a boss, and also replaces his platform with one closer to the lava. The design of the platform varies from copy to copy. Boss Blargg moves around the platform and shoots bouncing fireballs at the player like Bowser, and uses the circling fire object in the second fight, having it circle around itself. Defeating Boss Blargg gives you a star. Boss Blargg can not appear if there are no Blarggs in the level.

Reportings
However, due to the personalization of copies of Super Mario 64, sightings of Blargg could be noticed in some copies of the game. As it is a new entity on its own, it does not seem to be caused by Dynamic Level Rearrangement. However, the placement of Blargg can be affected due to the algorithmic change. It only seems to appear in the three stages listed above commonly. Unlike some anomalies, Blargg doesn't seem to have any malicious side effects or phenomena tied to it. No side effects were reported when the enemy had appeared.