Preheat oven to 350. If you havent already cooked your pasta, do that now. Once its cooked and drained, put it in a 9X13 glass casserole dish. In a bowl, combine the spaghetti sauce and the sour cream. If you are wanting this to be 5 ingredients or less, stop here. But if you want to add some garlic, onion, spices & seasonings add to the spaghetti sauce/sour cream combo now. We also add about cup of Parmesan cheese. Mix the sauce into the noodles in the dish. Cover with half the Mozzarella cheese you are planning to use. (we use a LOT of cheese) Layer the entire top of the casserole with pepperoni slices. Sprinkle the remaining cheese across the top. Put in the oven for 10-15 minutes or until cheese is melted. Serve immediately. For Freezing: If you make this to freeze, prepare as directed but DO NOT put in the oven. Cover and freeze. When ready to bake, remove from the freezer and allow to sit at room temperature for 30-45 minutes uncovered. Put in the oven at 350 degrees for 30-45 minutes.