Cook spaghetti according to package directions; drain.
Preheat oven to 375F.
In the bottom of a large bowl whisk the eggs and milk together and then mix in the Parmesan cheese, garlic, and oregano and then mix in the cooked spaghetti.
Spray a 13 x 9 casserole dish with cooking spray and pour the spaghetti mixture into the casserole dish.
Pour the spaghetti sauce over the top, and top with ½ of the pepperoni slices. Spread the mozzarella cheese evenly over the top and then top with the remaining pepperoni.
Bake for 25 minutes or until cheese is melted and starts to brown.