In a small skillet, saute celery in butter 5 minutes. Add onions; saute until vegetables are tender, 5 minutes longer. Place in a large bowl; set aside. , Preheat oven to 400°. Cut hot dogs into 1/2-inch slices. In the same skillet, saute hot dogs until lightly browned, about 5 minutes; add to vegetables. Reserve 1 cup. , In a large bowl, whisk eggs, milk, sage and pepper. Add remaining hot dog mixture. Stir in cornbread mixes. Add 1-1/2 cups cheese. Spread into a shallow 3-qt. or 13x9-in. baking dish. Top with reserved hot dog mixture and remaining cheese. , Bake, uncovered, until golden brown, about 30 minutes.