Preheat oven to 200 degrees F. In a small bowl, combine salad dressing mix, dill, lemon-pepper and garlic powder. Set aside. In a very large mixing bowl (or two large mixing bowls), combine oyster crackers, popcorn, fish-shaped crackers and pretzels. Make a well in cracker mix. Spray lightly with butter-flavored spray. Stir and spray again. Repeat 2 or 3 more times or until mix is very lightly coated with spray. Place cracker mix into 2 zip-top bags. Divide seasoning mix between the two bags. Seal and shake bag to coat cracker mix with seasoning. Pour into two 9-x13-inch baking dishes. Bake for 1 1/2 hours, stirring every 30 minutes.