Since E3 this year, when we first learned that Mario's magical hat Cappy would allow our hero to take possession of creatures in the Mushroom Kingdom and beyond, some of the specifics of the mechanic have been a mystery. Is Mario inside of the hat which is on top of the creature? Is he inside of the creature and the hat is the only thing tethering him there? Well, we may finally have an answer thanks to a glitch where Cappy can actually kill Mario while he is taking possession of a creature.
— DefinitivNichtSascha (@NichtSascha) November 13, 2017
In the above video from Twitter user @NichtSascha, Mario forces a Piranha Plant to eat a rock, then possesses the plant, spits out the rock, uses two player mode to independently move Cappy away (showing that Mario can maintain his possession without Cappy as a tether), and proceed to kill the plant using Cappy. Doing so kills Mario, who was seemingly trapped inside the plant and not freed when it was destroyed.
After this, Cappy can continue to play the game, but is unable to stray far from the scene of the crime. If the player warps to another part of the map, Mario will thankfully return.
Mario Odyssey is an incredibly polished game, so I'm going to assume this glitch was actually an intentional feature, and get to work on some serious theory videos about what this means for Mario's overall lore ASAP.