Preheat oven to 350º F. Cooked spaghetti should be rinsed under cold water and drained well. Place in a large bowl and blend in beaten eggs. Set aside. In a large, heavy bottom sauté pan, melt butter over medium-high heat. Add ground beef and ground pork and cook 10-15 minutes, stirring constantly until well-browned. Season to taste using salt and pepper. Add onion, celery, bell pepper and garlic. Sauté 3-5 minutes, working well into meat mixture until vegetables are cooked and wilted. Incorporate flour well into the mixture. Add milk and bring to a low boil, stirring constantly to avoid scorching. Milk should thicken after coming to a simmer and create a white sauce. Add three cups of grated cheddar and melt into mixture, creating a cheese sauce. Remove from heat and season to taste with salt and pepper. Pour meat sauce over spaghetti and blend quickly. Pour into a 9"x13" Pyrex baking dish and top with remaining cheese. Bake uncovered 20-25 minutes or until cheese is bubbly and light brown. You can prepare the dish one night ahead and bake the next day. You may also wish to cook the casserole, allow to cool and cut into portion-size squares. Simply microwave to reheat and serve.