Suckage glitch

The suckage glitch is a glitch that allows the physics of the boundary surrounding the Metro Kingdom to be abused to send Mario flying to distant locations.

Explanation

The entirety of the Metro Kingdom is surrounded by an invisible barrier that behaves as a force field. Rather than simply stopping Mario when he touches it, as a regular wall would, it applies a force to Mario if he is outside its limits, and this force gets stronger the farther Mario is outside the boundary.

The interior of the New Donk City Hall Auditorium is actually located in the same scene as the mainland of the Metro Kingdom. When Mario enters the auditorium, the game simply moves Mario to a distant section of the map where the interior is located. However, this location is actually outside the kingdom boundary, so in order to prevent the force pushing Mario back toward the mainland, the game temporarily disables the force field. The trigger that causes the boundary to be disabled is Mario entering the loading zone to the auditorium.