It's easy, all you have to do is choose any quest and "boast" and you'll end up on the pedestal in lookout point with some NPC's cheering you on, step off the pedestal and use your spade to dig anywhere that's diggable. More NPC's will be spawned every time you dig. Do this enough and the whole screen will be filled with people.

If you go over 100 the frame rate will drop drastically and eventually crash. This is useful for showing off trophies or killing people for evil points.