Cellar Slide

Cellar Slide is an anomalous area that rarely appears in highly personalized copies. It is usually said to appear alongside a restructuring of the First Floor, replacing the staircase leading down to the Basement with a Star Door requiring all power stars that can be collected on this particular floor, curiously with the exception of 100 coin stars. The Cellar Slide then presents itself as the only means of reaching the basement.

The area itself manifests as a retextured Cool, Cool Mountain slide, now appearing as a cave like structure. The player spawns in a wooden house and at the end of the slide a "painting" such as the "painting" to Dire, Dire Docks can be used to access the Basement.

The usual secret path down the slide can not be used, instead going around the house the player spawns in reveals a way to ascend it and access a tunnel leading down to a boss fight against about 13 anomalous Abominations, appearing as Mr. Is, walking on Wiggler legs and individually behaving like Big Bullies. Defeating them reportedly rewards the player with a red coin of which the player can find 8 around this area to obtain a power star. Along the way, the player can supposedly find a yellow cap switch, which when pressed unlocks the Aegis Cap, also sometimes called the Guard Cap. This anomalous power up protects Mario from the next three hits he would have taken, although it ignores damage by drowning. The cap itself appears as a yellow helmet with the typical red M at the front. picked up, Mario is enveloped by a golden mist and his costume changes colors from red and blue to white and yellow. The cap appears to never run out of time, even in simulated instances in which time was sped up, the latest maximum recorded time, before the records of these experiments were destroyed, was apparently 33 years. It is believed that only taking exactly 3 hits while wearing the cap can terminate its effects.

Another power star can be claimed by reaching the end of the slide faster than another Mario, who waits at the spawn area. When interacted with, multiple dialogue boxes filled with indecipherable content appear and disappear rapidly, this process has been described as deeply disturbing. The race promptly starts after about 15-20 seconds, and the other Mario seems to behave just like the penguin. He will award the player the power star at the end without a word before entering the portal to the basement.