MarioMario54321 is a popular YouTuber. He's the fourth most subscribed Machinimist, next to Megaman765, (possibly) MarioMario761 & SuperMarioGlitchy4.
he was first known as Mario64 on Lemmy's Land when he was a child. After getting blocked from it after stealing artwork, he left in dispair, many believing he died. However, he later was "reborn" when he joined YouTube, becoming MarioMario54321.
He later met Mario himself and began his life in the Mushroom Kingdom, creating videos and attracting other YouTubers to the Mushroom Kingdom. Eventually, they where invited to the Star World to save it from the entity Mastar, went to Ztarragus's Island with Bomberman to collect Ztars and defeat the Ztar entity who owned the island, returned to the Star World and defeated Mastar again, and later to defeat the now full of anger creator of Star World society and the land, and had many more adventures, two more to the Star World. However, him and his friends had their major enemies, the Dopplegangers. After a long battle, including the takeover of the world, and both them and their enemies unable to die, they defeated the Dopples and MM stabilized the Dark Star X, the source of the Dopple's power and life, and merged him with his counterpart, the Light Star X, into Star X. Later, he helped save the Fourth Dimension from Dimentio and went to fight Novuscurous to save the Star World for a fith time.