Flooded Castle Event


 * "If your romp through the castle is to be interrupted by the dasterdly King Koopa raising the water levels, quickly jump into a painting to avoid drowning and stick it to the evil turtle!"
 * — An official letter from Nintendo regarding the "flooded castle" phenomenon

The Flooded Castle event is a scrapped storybeat in Super Mario 64 where Princess Peach's Castle would become flooded. The event would effect all areas of Princess Peach's Castle and force the player to swim through the rooms without drowning. Where this event would take place in the game is unknown, however some players claim to have activated the effect during gameplay.

Details
While the specifics of this unused event are unknown, the basic assertion is that all areas within Princess Peach's Castle will be faced with a rising plane of water which will force Mario to swim through the castle. The functionality of which appears to be tied to the moat, which does the opposite in lowering the water in the main game.

In the main game, the Castle Grounds, Castle Courtyard and Basement are the only locations in Princess Peach's Castle to have bodies of water naturally within their object sets. Because of this, these locations are the most commonly specified when recalling instances of the flooded castle phenomenon. In the Castle Grounds and Castle Courtyard, the water notably rises to meet the roof of Princess Peach's Castle, allowing the player to walk freely on the roof without risk of drowning. On the roof will be several Toads, who seem to repeat lines of dialogue they will say in other floors of the castle. In the basement however, the water does not stop rising and could potentially be fatal to an unprepared player.

Some people claim that the water is able to rise on other floors of the castle, which has seemed dubious due to the water not being loaded in on these maps in particular. The behaviour of the rising water on these floors are identical to that of the basement, meaning that the player could be unprepared for the rising water and drown within the castle walls. When the inside part of the castle is flooded, all objects seem to get removed such as doors and Toads.

Speculation
With the modern theories regarding Super Mario 64, many people attribute the flooded castle event to the existence of the Personalisation A.I.. They specifically claim that the strange behaviours, exceptions and technicalities regarding the event appear to link up with an A.I. mindlessly activating a long-since scrapped in-game event that was never meant to occur, being the water levels rising within Princess Peach's Castle. The reason that in floors where water isn't present are less likely to flood come from people believing that the A.I. has to manually add water to these levels in order to flood them.

Legacy
Because of the nature of the castle flooding at random, many players have sent letters to Nintendo of America asking for information or advice regarding the phenomenon. Unlike certain other conspiracies relating to Super Mario 64, Nintendo has officially acknowledged the flooding castle phenomena in response letters. These response letters refer to the castle flooding as a ploy by "King Koopa", and that they must enter a painting in order to prevent the castle from flooding.

A similar event occurs in Super Mario Sunshine after unlocking Corona Mountain, where Delfino Plaza is flooded. The way in which Piantas have to take refuge on the roofs is similar to the Toads that appear on top of the castle in the Castle Grounds, implying that they escaped the flooding of the castle. There's a chance that if this event was intentional, that the scrapped ideas relating to it were repurposed for the GameCube installment.

Trivia

 * A similar series of events happens in Promo show of SM64 : CLASSIFIED, where Luigi swims through a flooded version of the castle's basement. The chance of these phenomena being linked with one another is unlikely, as the sequence of events that lead up to these appear completely different.