I am God!
~ Mario.EXE
You're too slow? Wanna try again?
~ Mario.EXE after killing Luigi
Hello! Do you want to play with me?
~ Mario.EXE encounters Luigi

Mario.EXE also known as Plumber X is the main antagonist from the LouisVsFrost Game Mario.EXE The Game, he is an demonic entity who takes the form of Mario to play games in hell, when he takes Mario's likeness, he brutally starts killing all of Mario's friends, turning the Mushroom Kingdom into a living hell by enslaving all of beings into becoming his servants for eternity.

In Mario Round 2.exe, he was defeated by Mario who becomes Super Saiyan Mario with the Chaos Emeralds that he inherits from Sonic the Hedgehog, after being killed by Mario, all of victims including Mario's friends are returned back to normal with no memory of being brainwashed by Mario.EXE earlier. It is possible that Mario.EXE, now as a damned spirit will get his revenge someday on Mario by keeping him all to himself for homosexual reasons, similiar to Sonic.EXE who wants to keep Sonic the Hedgehog all to himself.

In AGK vs. Mario.EXE, Mario.EXE has possessed Mario's body and soul to make Leopold Slikk have nightmares, but Leopold is able to exorcise Mario.EXE out from Mario's body, forcing Mario.EXE's soul back into Hell, returning Mario back to his normal self with no memory of being possessed, then Mario thanks Leopold for saving his life from Mario.EXE's influence. Luigi is happy to see Mario returned back to his normal self and returns home with him.