Preheat oven to 400. Prepare a 3-quart dish with cooking spray; set aside. In a skillet, cook celery and onions until tender. Place in a mixing bowl; set aside. Cut hot dogs into quarters, then into thirds. Place in a skillet, cook until lightly browned. Fold into celery mixture; set aside. Reserve one cup mixture. In another mixing bowl, combine eggs, milk, sage, and black pepper. Fold in hot dog mixture. Stir in cornbread mixes. Add one and half cups cheese. Spread mixture into prepared dish. Top with reserved hot do mixture and cheese. Bake, uncovered for 30 minutes, or until golden brown.