Prepare brownie mix according to package directions. Stir in 1/2 cup chopped peanuts. Pour into a buttered 9" square baking pan. Bake in a preheated 350-degree oven for 24-27 minutes. Cool completely.
Slice 2 of the bananas and layer over the brownies. In a large mixing bowl, whisk pudding mix into the milk; beat until mixture just begins to thicken. Fold in 2-1/2 cups of the whipped topping. Quickly spread pudding mixture over the sliced bananas. Refrigerate for 30 minutes. Sprinkle remaining 1/4 cup peanuts over pudding mixture.
Using a decorating bag and an open star tip, fill with remaining whipped topping. Cut the brownies into squares and pipe each square with whipped topping. Grate the chocolate over each square. Slice the remaining banana and top each square with banana slice and strawberry. Serve immediately.