Wario (full name Wario the Plumber, also known as Wario Gaywalker or Fartudinous Lump of Poop) is a classic major character and one of the two secondary antagonists (alongside Waluigi) of the SMG4 series. He serves as one of the three main protagonists of the Waluigi Arc (alongside Mario and SMG4).
He is Mario's evil doppelganger and Waluigi's adopted brother. He and his brother are homeless crooked criminals who would gain money by illegal means, however, Wario is the more greedy and rude one. He is known for being a thief, robber, conman, and a bully. He has a love-hate relationship with Waluigi, but the two always get along. Sometimes, the bros would join alongside other villains for money, such as SMG3.
When Waluigi became a megalomaniac and disappeared in The Waluigi Arc, Wario fell in despair, and set off to find his brother and a therapist for the two of them. SMG3, who was a therapist during that time, helped the bros reconcile with each other. Since then, the two of them became better people to each other, while serving as crooks for most of their time.
The brothers haven't had many appearances in Season 9. As of SMG4: Super Challenge 64 Wario has been reduced into mostly minor roles and cameo appearences with rarely getting a major role, however he still appears more often than his brother.
In Nintendo canon, Wario is an obese, muscular, hot-tempered and greedy man, and Mario's yellow-and-purple clad arch-rival. Most of the time, he goes on adventures ranging from stealing treasure to running a microgame making company.
He sometimes helps the heroes in the Mushroom Kingdom on a few separate occasions, such as when he rescued Mario from Waluigi. However, he has also been the villain in a few bloopers, usually whenever he gets his hands on something that grants him power.
In SuperMarioGlitchy4's bloopers, most of his personality traits are unchanged, minus the head of the microgame company, which has barely appeared in his bloopers.
He is shown to love his brother Waluigi and is regretful for mistreating and bullying him, which leads to him losing his power of rejection and no longer turning people into T-Pose zombies.
The mainstream Wario's origin is unknown due to his creators at Nintendo not sharing much information about him. In the game canon, he was formely Mario's childhood friend who was extremely jealous of Mario's popularity. In the comic Super Mario Adventures, he hated Mario because he unintentionally mistreated him and accidentally caused him to suffer humiliating injuries during their childhood activities.
In SMG4's world, he lived in the WAA kingdom (a weird counterpart to the Mushroom Kingdom where all the residents had his cartoony nose) where he was Waluigi's childhood friend. However, the two fought over garlic ice cream, and it led to Wario being washed away and stranded in the Mushroom Kingdom. Without money or a home, Wario began commiting crimes and scamming people for their money for over 20 years. After stealing a golden statue from the Koopa king Bowser, he reunited with Waluigi (who was banished from the WAA kingdom), and the two became partners in crime ever since.
Wario was able to survive Mario's Pain Train, which was full of death traps. However, he was taken down by a minigun that shot numerous coins at him in Mario's Challenge and a rocket launched by his brother Waluigi which destroyed his kart in Stupid Mario Kart.
During the time in which he obtained the Super Mario Maker, he was able to torment Mario in a variety of creative ways.
Wario Head: Whenever aggravated by someone who makes one of his close ones (like his brother) sad, he would turn into a floating head of himself, and will chase and try to haunt the culprit. He does have a weakness though, which is sad moments, as he was quickly defeated by Mario Head, who used that ability in SMG4: War Of The Fat Italians 2020.