Prepare and bake the cake according to package directions, using at 13x9-inch cake pan. Let it cool for 15 to 20 minutes. Using the round end of a wooden spoon, poke holes in the cake every 1/2-inch to 1-inch.

Empty the pudding mix into a medium-sized bowl and add the milk. Whisk briskly for 2 minutes or until the pudding is dissolved. Evenly pour over the poked cake, filling the holes as much as possible. Place the covered cake in the refrigerator for 2 to 4 hours or until the pudding is set. 

Microwave the hot fudge topping in a microwave-safe container for 20-30 seconds, or until it is easy to pour. Drizzle the topping over the cake. Use the back of a spoon to spread it evenly. Spoon the cherry pie filling evenly over the chocolate layer.

Frost the cake with the whipped topping. Garnish with chocolate shavings and maraschino cherries. (Tip: Blot the cherries dry on a paper towel before putting on cake to avoid the liquid running all over.) Store covered in the refrigerator.