Is one of the main character of Super Mario 64 Bloopers. He is very dumb and violent, often leading himself and his friends into trouble. He also loves spaghetti, despite the fact he doesn't know how to make it himself. He's shown not liking his brother Luigi, and is very lazy.
Is the doctor version of Mario, and is about the same in terms of intelligence and competence. He sucks at being a doctor mainly by being distracted several times. He is the main character in Retarded64: A Dose of Dr. Mario and Retarded64: An Overdose of Dr. Mario. He's shown to be a seperate person from Mario as shown in SM64: Ssenmodnar 9 - Time Travel Edition and SM64: Super Mario RUN RUN RUN!.
Paper Mario is the paper variant of Mario who lives inside a book containing the Paper Mario universe. He usually appears in SMG4's earlier videos in the Paper Mario scenes and sometimes in the rare clips of Paper Mario Thousand Year Door. Paper Mario is rarely seen in any of the newer videos (save for a few cameos on in the videos and thumbnails for them). Paper Mario even got the major role in the 2017 video Stupid Paper Mario.
Bootleg Mario (Also known as Grand Dad) is a bootleg version of Mario. He first appeared in SM64: THE BOOTLEG DIMENSION where he was freed from the Bootleg Dimension by Mario. He has the ability to turn characters and landscapes into bootleg version through touch or by zapping them with a laser. He appeared in SMG4: Welcome To The Kushroom Mingdom as the"Ghost of Sh!tty Games" where he grants SMG3's wish to build a kingdom similar to the one he lives in except "cooler".
Mario Head (also known as Mario's Ugly Head or The Giant Floating Mario Head) is the head version of Mario from Mario Teaches Typing 2.
He's similar to regular Mario, as he likes spaghetti about as much as him. But is shown to be a lot smarter than him.
In The Grand Mario Hotel, it's revealed that he HATES it when people use bad grammer.
Hobo Mario (Also known as Ugly Mario) is an ugly and distorted clone of Mario. He was first appeared in Casino, Cards and Chaos
Baby Mario is the baby version of Mario. He's sometimes depicted as a sprite other times a 3D model. He made his first appearance in Super Mario 64 Bloopers: The Babysitters.
Smart Mario is taller, more realistic version of Mario with glasses and a graduation hat, and as the name suggests he's a lot smarter than regulars Mario.
He so far only appeared in The Grand Mario Hotel, where he was the first mario variation to be meet SMG4's Mario.