Mario is in endless loop of doing the same thing, Collecting all 120 stars, doing the same thing in the same box. He has developed Apeirophobia 
the Fear of Infinity and becoming self aware. As the Skull of a Grey Fox floats and watches him. Not harming or speaking to him, just watching him seeing his dead Body, or dead bodies twitch and shake while he stares into Mirrors. As there are infinite castles and islands. Having infinite Mario's become like him. He stands on the roof of the Castle.