One thing that is consistent throughout the many years of South Park's run is that the adults are generally pretty stupid and the show's universe is surreal and otherworldly. Businesses and schemes from the South Park adults are successful when they really shouldn't be, Kenny dies and revives all the time, and Jesus and Satan walk through the town like it's nothing. According to a few fans, there's a simple explanation to all of this: South Park is purgatory for all the idiots in the world. It is a place where dumb people have free reign to be completely ridiculous without bothering all the 'smart' people. This explains why Jesus and Satan make appearances as they're both trying to get these idiots to go to Heaven and Hell respectively. As for the children, the theory goes on to explain that they're young angels sent to South Park in order to learn humility, how to become decent people, and how to deal with the idiocy that is steadily growing on Earth. Of course, not all of these young Angels remain pure and some do turn bad, hence why Cartman is the jerk that he is and why he is seen as the outcast of his peer group.