Editor's Favorite; Make Ahead
Prepare cake according to package directions in a greased 13" x 9" pan. Cool completely in pan on a wire rack.
Gently poke holes in top of cake, using the end of a wooden spoon (wipe spoon clean after each hole). Combine sweetened condensed milk and caramel topping in a small bowl; slowly pour over cake. Spread whipped topping over cake. Sprinkle with crushed candy. Cover and chill until ready to serve.