Prepare and bake cake according to package directions for an 8-in. square baking pan. Cool on a wire rack. Prepare pudding according to package directions.
Cut cake into 1-1/2-in. cubes; place half of the cubes in a 3-qt. trifle bowl or large glass serving bowl; lightly press down to fill in gaps. Top with half of the whipped topping, pudding, caramel topping and toffee bits; repeat layers. Cover and refrigerate until serving. Yield: 16 servings.