Field of Bowsers

The Field of Bowsers is an anomaly that occurs in the Castle Grounds. It was reported by Reddit user u/adriank060 on the 8th of July 2020.

Description
When the anomaly occurs, the player will find four or five Bowsers in the Castle Grounds. Their behaviour is similar to that of a Goomba; they wander around aimlessly until they become aware of Mario's presence. When they see Mario, they begin chasing him in a similar manner to how Bowser does in the second and third Bowser fights; they do this at a slower pace than in the fights which allows Mario to flee and they do not stop until Mario somehow gets out of range (i.e. via the cannon), enters a loading zone or dies. At the same time, they attempt to burn Mario with their fire breath. It is currently unknown if there is a way to defeat them.

How to Find It
Due to there only being one recorded case of this anomaly, the method used to find it is largely unknown. However, according to the original poster, their friend who owned the game claimed that it occurred when she finished the game. This may mean that it's a result of a high amount of personalisation due to how much data the AI may be able to gather from somebody who has beaten the game legitimately. It may also just be a bit of extra challenge given to a player who has proven that they are skilful at the game.

Theorising


It's possible that in an earlier version of Super Mario 64, Bowser was intended to chase Mario in the Castle Grounds. This is because of the image which appears on the box art: it depicts Bowser chasing Mario whilst using fire breath, similarly to the Field of Bowsers anomaly. This may provide an explanation as to why the Bowsers in the anomaly behave in such an odd way; the AI may have modified them when performing DLR but why would it do that instead of just utilising the regular Bowsers? If this is correct then the behaviour Bowser had in the Castle Grounds may still remain in the game's files for the AI to utilise.

Furthermore, the geography of the field appears to be similar to the Castle Grounds' – Mario and Bowser are running on a slope with a steeper slope behind them; this seems similar to the slope just in front of Mario when he spawns after a file is selected. The sky shown in the art also seems akin to that of the Castle Grounds' skybox, although this may merely be coincidental. Oddly enough, however, the trees that are present in the Castle Grounds appear to be missing.

If this is correct then it is probable that Bowser's presence in the Castle Grounds was cut fairly late into development as it would have happened after the cartridge art had been finalised. On the other hand, if this is incorrect then the question of what the box art depicts remains unanswered.