The Mario that the show focuses on (Interdimensional ID: Mario #8052011, known as Stupid Mario, as revealed in The Grand Mario Hotel, or as he calls himself, Mario Sexy the Plumber) is often portrayed as the dumb guy of the show, and a morbidly obese spaghetti addict. While he seems to think he is popular and has lots of swag (which is true as he has a fan club), Mario is in reality an attention-hogging, possibly gay and pedophilic streaker who has been arrested several times. In addition, Mario has been depicted as a pervert, zoophile, prostitute, drug addict, and drunkard.
Because most of the aforementioned traits are played for comedy, Mario is the protagonist of many bloopers. While he can act somewhat bipolar, and is usually enraged by the slightest things, Mario is often cheerful to the point of annoyance.
Mario wears a long-sleeved red shirt, blue overalls with yellow buttons, brown shoes, and with gloves. He has a red cap, brown hair, a black mustache and blue eyes. He is shorter than his younger brother Luigi.
He is morbidly obese.
In Nintendo canon, Mario is a friendly plumber who helps anyone in need, devotes most of his time to rescuing the princess of the Mushroom Kingdom, and participates in sports matches, kart races and "parties" often.
In SuperMarioGlitchy4's bloopers, Mario looks the same. However, unlike his game counterpart, Mario is an arrogant, lazy, ignorant and gluttonious moron who cares more about himself and his favorite dish, spaghetti. In fact, he's so addicted to the food that he steals it from other people, refers to it either as his girlfriend or wife, and humps it. Additionally, the mere thought of losing spaghetti causes him to either cry in frustration or commit suicide. His laziness makes him an antisocial person and he really hates exercising. Mario also refuses to help out his friends often, even in life-threatening situations, and is either forced or persuaded with spaghetti into helping. Despite this, he cares deeply for his friends and family.
One of his most defining traits is his stupidity, which makes his friends' lives miserable without Mario himself realizing it. Only a few of his friends understand him and accept his stupidity, whereas everyone else hates and despises him for it. According to SMG4, Mario did not know what 1+1 was and didn't know any number past 10 (aside from 1 million), and he makes idiot plans which often somehow work out of sheer dumb luck. As the series progresses, Mario gets more and more retarded, to the point where he forgot how to type or how to count. He however, openly refuses to admit his stupidity and claims to have an IQ of 200. He also sometimes uses stupidity to his advantage and there were rare moments where he acted with great intelligence.
Mario also has short temper, which landed him in conflict with many characters. His temper is so short that he often lashes out at people (including his own brother Luigi) when they annoy him, tries to get revenge ( a example was when a Big Chungus ate his spaghetti) and beat the living crap out of them. He is also a sore loser, and he gets furious when losing in something.
Mario's personality in the bloopers are overall just used for comedy, and the reason for it is unknown.
Like his mainstream counterpart, Mario has a multitude of strengths and powers.
Here are his primary shown powers:
Superhuman strength: Mario has been strong enough to punch people several feet away, and lift Bowser, who weighs over 300 pounds. He also punched a pilot straight through the window and down to the ground in Super Happy Magical Fun Fun Island, and once even lifted King Bob-omb (calculated to weigh 30 tons). He can also rip out a control panel of train and even throw a weight-lift into the sky. After launching Fishy Boopkins in the sky, he ended up making a plane crash into E. Gadd's workshop.
Superhuman endurance: Mario has survived falls from great heights, explosions, getting attacked by Bowser, getting crushed, blows from SMG4 (about as strong as him), and even car crashes, all barely fazed.
Pyrokinesis: Much like his own games, he has shown the ability to manipulate fire.
Hand-to hand skill: He is a master at unarmed combat, as shown by his many battles, with him winning most of them. He has his own unique style, with very fast and powerful punches and kicks and tackles.
Giant size and strength: In Ssenmodnar 10, Mario used a Mega Mushroom to grow into Mega Mario, a power-up form who is bigger, stronger and tougher than the base Mario.
Coldness survival: In Snowtrapped, in some clips, Mario is seen naked in the freezing cold a few times, without any adverse effects.
Great rapper: In War of the Fat Italians 2015, 2016, 2017, 2018, as well as Supah Star Rap Battles of Epicness, Mario has demonstrated great rapping skill.
Computer hacking: Despite normally being unintelligent, Mario was shown to be perfectly capable of hacking into computers in Mariotube 2. However, he needed to break into YouTube Studio in order to do so.
Of course, Mario has weaknesses (though comparatively few compared with many characters):
Slow speed: Due to his high weight (at least 12,000 pounds which equals 7 tons), he is slow on his feet, as shown in 101 Ways for Mario to Die, Retarded64: The 1337 Police, and several other bloopers, though this isn't much of a flaw compared to his biggest weakness. However, he was shown to be agile enough to avoid being flattened by the Hamburger Supreme in Super Mario Jackass.
Stupidity: Mario is one of the most stupid characters (if not the most stupid character) in the series, not even knowing what 1+1 is until Baldi taught him math. It is so far his biggest weakness, as it cost him quite a few battles, despite his strength. However, Mario sometimes does shows signs of intelligence in some episodes, with the biggest example being Stupid Mario Stupid Show.
Mario and Peach have had sex before. A few times, actually.
Mario (outside of the SMG4 universe) is classified as homo nintendonus. This is a fact that was revealed in 2014.
In Dreams, it is revealed Mario has a phobia of old people after his 2nd dream.
The reason SMG4 made Mario a mentally retarded character like Homer Simpson from The Simpsons or Peter Griffin from Family Guy was because he felt that using an "normal" or "heroic" personality would be boring. Incidentally, his author avatar has that personality.
Mario is a tiny bit transparent when the SM64 model is used, this can be found in Mario the Waiter after Luigi goes to cook Mario's burrito with spaghetti in it, with the pyro from TF2 being slightly distinguishable.