Originally a nickname for Hamilton, Ontario, Canada; A city or town that has a higher than normal rate of mullets per capita. This is presumably caused by the complete lack of self worth by the individuals who live in these places. High rate of white trash. Usually must imply a real dump of a place as well.
Examples of Mulletvilles in fiction: Trailer Park Boys, Sunnyvale Park
Examples of actual Mulletvilles: Hamilton Ontario Canada
"When rolling into Hamilton, one can see and smell the heavy factory air, flaming, smoking stacks erected from mills that devirginize the lakeview, followed by a non-stop supply of grimy, drug addicted, unstable, ugly, miserable, ignorant people that populate this low life metropolis. Much of the regular population blend in well with the homeless who walk next to them. The better dressed usually choose a wardrobe inspired by Trailer Park Boys or Eminem. The corpses of businesses that died lay lifeless on the sides of the main roads. That is when the driver turns to you and says "Welcome to Mulletville pal. And your heart sinks."