Preheat oven to 350°F. Spray medium casserole dish with nonstick spray.
In small bowl, stir crackers and butter until well combined.
If leftover potatoes are cold, place in a medium microwave-safe bowl and microwave 1 minute to soften. Add sour cream, garlic powder and pepper to potatoes; stir until well combined.
Reserve 2 tablespoons each cheese and bacon. Add onions, parsley and remaining cheese and bacon to potatoes; stir until well combined.
Transfer mixture to prepared casserole dish and sprinkle with cracker mixture and reserved bacon and cheese. Bake 25 minutes or until heated through.