Break spaghetti into small pieces, 2 to 3 inches long. Cook as directed on package; drain well. Cool. Add chopped pepper, onion, celery and tomatoes. In separate bowl mix together sugar and dressing. Pour over spaghetti and vegetables. Stir to blend well. Cover and refrigerate overnight. Stir again before serving. Add grated cheese, if desired. May be stored for several days in refrigerator. Yields 6 servings.