Eric Cartman is the "Fat Kid" in the group and the others are constantly making fun of him about his wieght. When Scott Tenorman doops him out of $16.12 Cartman becomes determined to get him back. As Scott shows up to Cartman's party later that week, he discovers that there is more to "Chili con Carne" than he previously thought. Basic rule, don't f*ck with Cartman.
Source: South Park Studios