Preheat the oven to 425 degrees F (200 degrees C). Prepare instant mashed potatoes according to package directions. Stir in half of the Cheddar cheese, bacon bits, and green onions.
Cut the pizza crust dough in half, and spread into the bottom of two 8-inch round pans. Bake for 4 minutes in the preheated oven, until about halfway done. Spoon the potato mixture over each crust. Sprinkle remaining Cheddar cheese over the top.
Bake for an additional 5 minutes in the preheated oven, until crust is golden, and cheese is melted. Let cool for 5 minutes before slicing and serving. Top with sour cream to taste.