Preheat oven to 375 degrees F. Spray 13x9-inch glass baking dish with cooking spray. Combine baking mix and milk in medium bowl; stir until soft dough forms.
Drop dough by spoonfuls on bottom of baking dish (will not completely cover bottom). Spoon 1 can spaghetti and meatballs over dough and sprinkle with 1/2 cup cheese. Top with remaining can spaghetti and meatballs, remaining 1/4 cup cheese and pepperoni.
Bake 20 to 25 minutes or until dough is done in centers and browned.
Add your favorite pizza toppings, if desired. Get the kids involved with preparation; they can prepare the dough, layer the ingredients and top the dish with pepperoni.