Fatso has a lower IQ point than the other two and will literally eat everything in sight. Sometimes, Stinkie and Stretch tire for Fatso's stupidity. However, he is signifiantly smarter in the self-procaimed prequel than the 1995 film.
Fatso also felt a familial connection to Casper out of the others, stating it was like being a family with him. Eventually, this comes true when they adopt Casper as their nephew. Also Fatso is the only one Casper calls "Uncle Fatso" in A Spirited Beginning.
