South Park has four main child characters: Stan Marsh, Kyle Broflovski, Eric Cartman, and Kenny McCormick. These four boys form the central group around which the series’s early stories were built.
Each character fills a distinct role. Stan is often the relatively ordinary viewpoint character, while Kyle frequently provides a moral or skeptical perspective. Cartman is aggressive, selfish, and deliberately outrageous, and Kenny is the poor, muffled-speaking friend whose repeated deaths became an early signature gag. Their contrasting personalities allow the show to satirize politics, religion, school life, family dynamics, and popular culture.
The number four refers to the core group, not every important child in the series. Butters Stotch, Wendy Testaburger, Bebe Stevens, and Tweek Tweak are recurring and sometimes central characters, but they are generally classified as secondary or supporting characters. Butters became especially prominent after Kenny’s temporary departure during season six, which can make viewers remember a larger regular ensemble. The original concept, however, was explicitly built around four children.