Bring a large pot of lightly salted water to a boil. Stir in macaroni, cook for 8 to 10 minutes, until al dente, and drain.
In a skillet over medium heat, cook the Italian sausage and onion until sausage is evenly brown and onion is tender. Drain grease.
In a bowl, mix the pizza sauce, tomato sauce, and milk. Stir in the sausage and onion, pepperoni, mushrooms, olives, and Canadian bacon. Gently mix in the cooked macaroni until evenly coated. Transfer to the prepared baking dish.
Cover, and bake 30 minutes in the preheated oven. Remove cover, top with cheese, and continue baking 15 minutes, until cheese is melted and bubbly.
