Preheat oven according to brownie mix package directions. Line 13 x 9 x 2-inch baking pan with foil, extending ends over sides.
Prepare brownie mix according to package directions. Stir in peanut butter chips. Pour into prepared pan. Bake according to package directions. Cool completely on a wire rack.
Lift foil out of pan. Invert onto cutting board. Remove foil. Cut brownies into 3/4-inch pieces with a sharp knife.
Coarsely chop 20 peanut butter cups, reserving 4 for garnish.
Combine pudding mix and milk in large mixing bowl. Beat on low speed for 2 minutes, or until thickened. Add peanut butter and vanilla. Beat until smooth. Gently fold in 2 cups whipped topping.
Place half of brownies in bottom of trifle bowl or large glass bowl. Top with half of chopped peanut butter cups. Spoon on half of pudding mixture. Repeat layering. Top with remaining whipped topping. Slice each of remaining 4 peanut butter cups into 4 long pieces. Arrange on whipped topping to garnish. Chill.