There have been many variations of Mario from many alternative universes and Mario games within the Super Mario franchise and the SMG4 continuity. This was fully shown in SMG4: The Grand Mario Hotel.
Mario #8052011 of the SMG4 Universe is the central character and one of the two main protagonists of the SMG4 series. He is very dumb and can also be 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 to not like his brother, Luigi, and is very lazy, though he starts to be more caring to his friends.
Dr. Mario 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 R64: A Dose of Dr. Mario and R64: An Overdose of Dr. Mario. Although in some bloopers he is just Mario wearing a doctor coat such as SMG4: Mario University and SMG4: The Melancholy of Fishy Boopkins, in other bloopers, he's a separate character such as SM64: ṩṩἔᾗмὄḋᾗᾄʀ 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. Paper Mario is the main protagonist of Paper Mario series. 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 in the videos and thumbnails for them). Paper Mario even got the major role in the 2017 video SMG4: Stupid Paper Mario.
Bootleg Mario (Also known as Grand Dad) is a bootleg version of Mario. He is the protagonist of the Mario-themed bootleg game, 7 Grand Dad, which is based of the 1991 NES game The Flintstones: The Rescue of Dino and Hoppy. He first appeared in SMG4 series in SM64: THE BOOTLEG DIMENSION where he was freed from the Bootleg Dimension by Mario. Since then, Grand Dad is considered to be the arch-nemesis of Mario. He has the ability to turn characters and landscapes into bootleg versions 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 more "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 just as much as him. But he 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 grammar.
Animatronic Mario is an animatronic husk that Mario was programmed into alongside the violent Spaghetti.exe executable file. He made his first appearance in R64: Revenge of Freddy's Spaghettria.
Animatronic Mario's personality is the same as regular Mario, but he can get hostile immediately if the spaghetti.exe program is operating.
Hobo Mario (Also known as Ugly Mario) is an ugly and distorted clone of Mario. He first appeared in SM64 Bloopers: Casino, Cards and Chaos. Hobo Mario's model originated from The Simpsons Game. His personality is loosely based on John Herbert from Family Guy.
Baby Mario is the infant version of Mario. He is a major character in the Yoshi's Island series. He is sometimes depicted as a sprite or, at other times, a 3D model. He made his first appearance in Super Mario 64 Bloopers: The Babysitters.
Sometimes Mario will scream "I won’t live to see my Baby Mario!".
Various multi-colored Marios have appeared throughout the series, some representing machinimists such as MarioMario54321 and SMG4 himself, while others are completely original to the series, such as Crazy Toilet Dude and Cap'n LardButt. Aside from SMG4 and his evil doppleganger SMG3, FightingMario54321 and Nintendofan997 appear the most often in later videos whenever they do, but they have all become noticeably more absent over the years to make room for other characters.
They play a major role in The SMG4 Movie: 10 Year Anniversary Special, where it is revealed that the in-universe cause of their absence was that a virus called Zero abducted and killed them in a desperate search for the original Mario. At least in SMG4 and SMG3's case, Mario's life energy being drained apparently caused the two SMGs to begin losing their forms. The rest of the recolors were used as zombified minions by Zero to stop the rest of the gang from putting an end to his genocide. When Zero was finally defeated, the recolors were miraculously cured and relocated to Bloopersville.
8-bit Mario is a Mario that first appears in Super Mario 64 Bloopers: Clone O' Mario. He speaks like a microwave.
Metal Mario is a metal version of Mario who lives underground in a cave. He is know to collect Rocks for some unknown reasons.
Bob Hoskins Mario
Bob Hoskins Mario was unleashed in SMG4: Stupid Mario 3D All-Stars. He's based on the actor Bob Hoskins, who portrayed Mario in the 1993 film, Super Mario Bros.. He used his movie as a weapon due to how terrible it is. He was killed by Rock Mario.
Clown Mario was first seen in SMG4: Mario vs IT 🤡 as an vision by It. He's based on Mario wearing the Clown outfit from Super Mario Odyssey. He attacked Mario in the kitchen. SMG4 was unable to help, somehow incapable of telling whether Clown Mario was the fake or the real Mario. Boopkins saw an electric current and used it to revive Toad (Who was dead at the time). This caused Toad to go on an adrenaline rush, singing in such a horrible voice that Clown Mario's head ended up exploding.
He returns in SMG4: Stupid Mario 3D All-Stars as one of the Mario’s unleashed.
Don Mario is the one who runs the Grand Mario Hotel. He's Dumbledore from the Harry Potter franchise with Mario's mustache and cap.
In The Grand Mario Hotel, Don Mario decided to invite SMG4's Mario to the hotel, which leads to him getting injured and unable to run his hotel. He tries to get Mario to tell Smart Mario to run the hotel, but Mario assumes he wants him to run the hotel. After all the other Marios retaliate on him, he and Smart Mario resurrect Don Mario using a 1-Up Mushroom.
Dream Mario is an idealized version of Mario in Peach Toadstool's dream. He is a shirtless, muscular version of him. His only appearances so far are SMG4: Marioception and SMG4: 3 MILLION SUB FAN COLLABORATION!.
Kawaii Mario is an anime-like variation of Mario. He wears a dress, pink ribbons, and has rosy cheeks. He is a huge reference to Madoka Kaname from Madoka Magica, this is because Kawaii Mario is dressed up as her.
A LEGO version of Mario, his appearance is based on the official release of LEGO Super Mario Adventures.
He first appears in SMG4: Stupid Mario 3D All-Stars.
Mario's Brain lives inside of Mario and is one of the main sources of Mario's body, controlling most of him. Luigi bribes it to attack the Virus.
He first appears in SMG4: Mario's Inside Story.
Mango is the main antagonist in SMG4: The Tari Abnormality.
Mango was a character from the Super Smash each other in the ass Bros. series. According to Mango himself, he doesn't like fighting, yet has been doing so non-stop for 56 years straight. Worse, the developers keep "nerfing" him with every game. Thus, Mango considers his life an "infinite hell". He was shot by Mario who showed no sympathy for his backstory but returned in SMG4: Stupid Mario 3D All-Stars.
Princess Mario is Mario in Peach's bridal dress from Super Mario Odyssey.
He first appears in SMG4: Stupid Mario 3D All-Stars.
Shadow Mario is a doppelgänger of Mario who portrayed as an antagonist of the game, Super Mario Sunshine. He appears in Mario's EXTRAS: The Grand Mario Hotel, where he writes Mario Sucks on purpose to get the Marios in a fight.
Skeleton Mario is a skinless version of Mario. He appears to have the same power as Sans.
This uh... Mario
This uhh... Mario is a unidentified version of Mario who appeared as minor character in The Grand Mario Hotel as a guest.
Soccer Mario is the Super Mario Strikers version of Mario.
He asks Mario if the Hotel has any classes. Mario directs him to the syndicated drowning class. Soccer Mario happily joins.
Smart Mario is a taller, more realistic version of Mario with glasses and a graduation hat, and as the name suggests, he is a lot smarter than stupid Mario.
He only appeared in The Grand Mario Hotel so far, where he was the first Mario variation to meet SMG4's Mario.
Smash 64 Mario
Smash 64 Mario is the original Super Smash Bros. version of Mario.
Super Mario Maker Mario
Mario in his outfit from Super Mario Maker.
Wendy's Toy Mario
Mario as a Wendy's Kids Meal toy. He first appears in SMG4: Stupid Mario 3D All-Stars.
The Mario Mask is a mask which looks just like Mario.
It debuts as the main antagonist of SMG4: Mario's Mask Of Madness.
Super Mario is a non-canon version of Mario that only appears in SMG4 2020 COLLAB SPECIAL in a brief clip where he comes out of a warp pipe only to see "Stupid" Mario eating spaghetti before deciding it tastes like sh*t and walked away. Then after seeing Tari and the others he freaked out and used a question block to go into a warp pipe out of confusion which confused Tari and the others
- Mario is the first character in the SMG4 Series to have multiple alternative version across the multiverse.