In a large skillet, cook the beef, onion and garlic over medium heat until meat is no longer pink; drain. stir in salt and pepper; set aside. Cook spaghetti according to package directions; rinse in cold water and drain.
In a bowl, combine eggs and milk; stir in spaghetti. Transfer to a greased 13x9-in. baking dish. Top with spaghetti sauce, beef mixture, pepperoni, mushrooms and olives; sprinkle with cheese (dish will be full). Bake, uncovered, at 350° for 40-45 minutes or until bubbly.