Sergio is a fan character in the series. He's a protagonist in Seasons 1 and 2.
Sergio always thought of himself as a hero, though that wasn't the case. When he is told that he and the other fan characters had to help save the world, he goes on a journey with Mario and the rest of the team. Sergio's team encounters the likes of Petey and Bowser. He helped Mario faced Bowser the first time, though the second time he wasn't allowed to. Sergio seems insulted because Masterells and Frosty always ruin his moment of becoming a hero. When the team sees Shadow Mario the second time, Sergio charges at Shadow Mario in order to "save the day". Sergio will always try to be a hero, no matter what.
He is cool to hang out with, He will only get mad if he is getting offended or will play the hero.
Hammer: Sergio can use his hammer to attack attack enemies or deflect projectiles. Though to a weaker extent due to him being less experienced in using it to Luigi or Mario
Electrokinesis: Sergio can manipulate electricity and use it on enemies to injure them. Like last time, due to being less experienced than Luigi, his skills of it are less.
- Sergio always had humerous moments in Season 1. An example of this is when he had poop on his shoe caused by WEEGEE.
- Sergio is somewhat like Luigi: Both want to be number 1, both have their moments, and both are sausage boys.
- Sergio is the first fan character to be in a tag team with a main character.
- Apparently, Dark Chaos is Sergio's cousin, though it has never been mentioned in Season 1 or Season 2.