SuperSwagTubbie is a Teletubbie and the main antagonist in R64: Mario Simulator. Mario steals her glasses like a douchebag. She reappears in front of Peach's Castle getting retaliation on Mario when she gets an army of Teletubbies to kill him. She is also the final boss.
According to the rule according to which a name in plural which ends in "-ie" ends in "-y" in singular, the name of this Teletubby should be "SwagTubby" and not "SwagTubbie". It's probably a mistake made by SuperMarioGlitchy4, who always writes "Tubbie" instead of "Tubby" in singular.
This character is dead with the others when Mario throws the cartridge of the game into the Sun. In other words, SwagTubbie is lost forever. Despite this, she has made a few more appearances after this.
If one looks closely, SwagTubbie has a Ferrari 360 Spider.