Originally pizza had tomato sauce, some kind of meat and mozzarella cheese. But today, anything goes. You can put brown gravy, slices of meatloaf, and mash potatoes on a circle of dough if you choose to and call it pizza. Purists will argue with you that it is not pizza. But eventually you reach the point where you can put so much on the dough, that you lose the originally taste and flavor you were going for. More is not always better. Brown gravy, milk gravy and tomato gravy on that meatloaf pizza destroys the total concept of the original idea for a different type of pizza.