For the burgers: Preheat the grill to high heat. Mix together the beef, onions, breadcrumbs, mayonnaise, salt, garlic, celery salt, soy sauce and eggs in a large bowl until thoroughly combined. Form the meat into 5-ounce patties, and then cover and set aside in the refrigerator while preparing the toppings.
Let the burgers come to room temperature before cooking, and then grill until medium-rare. Meanwhile, heat a nonstick pan and cook eggs to over-easy, for topping burgers.
For assembling: Top the burgers with American cheese, bacon, spam, Portuguese sausage, over-easy eggs and lettuce. Serve with the Muffler Magic Sauce on toasted buns.
Mix together the ketchup, mayonnaise, mustard, vinegar, agave and cayenne until thoroughly combined. Season with salt and black pepper.