Mongolians

 The Mongolians are first seen in the South Park Episode titled Child Abduction Is Not Funny. They are the primary antagonists for the owner of City Wok as he had been told to build a wall around South Park to keep out intruders and they constantly destroy it. The mongolians are almost constantlyu outsmarting the owner of City Wok.

Later in the Child Abduction Is Not Funny episode the children become part of the Mongolian tribe and help to destroy the wall.

In the end of the Child Abduction Is Not Funny episode all the parents learn that the Mongolians had the right idea, that you cant just put up walls because putting up walls never helps anyone and that it's wrong.