Prepare the Yellow Cake Mix to directions on the back of the box using either 2 8 or 2 9 inch round cake pans. Let cool completely on wired rack.
Place the bottom of one of the cakes on cake stand of your choice. Carefully cut off the top of the cake so you have a flat surface. (Quick Tip: if you are concerned about getting your cake stand dirty, cut small strips of wax paper to line the bottom of the plate, later you can slide them off and boom! no mess.)
Hollow out the inside of the cake, to about 3 inches from the sides. Make sure not to cut all the way through to the bottom. Using a spoon makes this easy. Fill the inside of the cake with the candy of your choice. Carefully frost the cake part of this bottom layer. The frosting is more easily spreadable if you microwave it with the foil wrapper OFF for 10 seconds. Mix frosting with a spoon or spatula and spread on a thick layer. Add more candy in the center so it fills in the hole. Repeat the process of cutting off the top of the second layer of cake to make a flat surface. Place second layer CUT SIDE DOWN onto the candy and frosting.
Frost entire cake with remaining frosting. Cut to serve and surprise! Enjoy.