Heat oven to 350°F (325°F for dark pan). Grease 13x9-inch pan with cooking spray or shortening.** In large bowl, make brownie mix as directed on box using oil, water and eggs. Stir in 1 cup of the chocolate chips. Spread batter evenly in pan. Bake 28 to 30 minutes. Cool on wire rack while making topping.
In medium microwavable bowl, microwave caramels and water on High 1 minute. Stir; continue to microwave in 15-second increments, stirring after each, until caramels are completely melted and mixture is smooth. Stir in broken pretzels until well coated. Spoon and spread carefully over cooled brownie layer.
In large bowl, mix melted butter and powdered sugar until smooth. Stir in peanut butter. Stir in broken cereal until well blended. Spread or pat over caramel layer.
In small microwavable bowl, microwave remaining 2 cups chocolate chips on High 1 minute. Stir; continue to microwave in 15-second increments, stirring after each, until chocolate is melted. Spread over cereal layer. Refrigerate until chocolate is set and caramel mixture in center is firm, 2 to 3 hours. Let stand at room temperature 10 minutes before cutting. Cut into 6 rows by 4 rows.