Preheat oven to 375. In a medium bowl, stir together chopped meatloaf, soup, mustard, and ketchup; press into bottom of unbaked pie shell. Set aside.
Stir bacon crumbles into macaroni and cheese. Spoon evenly over meat mixture; top with french fried onions. Bake in preheated oven for 35-40 minutes. Slice and serve hot.