Preheat the oven to 350 degrees F (175 degrees C). Cook bacon in a large deep skillet over medium heat until crisp. Drain, crumble and set aside.
Spread the pizza dough out on a lightly greased baking sheet. Spread mashed potatoes over the dough, leaving a small crust around the outside if you want. Sprinkle the cheese and bacon evenly over the potatoes.
Bake the pizza in the preheated oven until the cheese is melted and bubbly, about 20 minutes. Let cool for 2 minutes, then slice into wedges and top each one with a small dollop of sour cream.