Cook spaghetti according to package directions; drain. Return spaghetti to saucepan. Stir in the chicken, spinach, soup, mayonnaise, sour cream, celery, onion, green pepper, pimientos and lemon-pepper.
In a small saucepan, whisk flour and milk until smooth. Bring to a boil over medium heat; cook and stir for 2 minutes or until thickened. Stir in bouillon. Pour over spaghetti mixture and mix well.
Transfer to a 13-in. x 9-in. baking dish coated with cooking spray (dish will be full). Top with mozzarella cheese, bread crumbs and Parmesan cheese. Bake, uncovered, at 350° for 25-30 minutes or until heated through. Yield: 10 servings.