Mix cake mixes according to directions. Pour evenly into 2 10" square greased baking pans. Bake according to recommended oven temperature and time until cake tester comes out clean. Cool on wire rack. Using electric mixer combine frosting and confectioners sugar. Mix all but 1/3c frosting with small amount of black food dye to make it gray. Dye the other 1/3c frosting green.
Stack cake layers on cake board covered in freezer wrap (glossy side up) with a thick layer of gray frosting in between. Cover the cake with gray frosting. Divide the fondant into two halves (save back a little). Dye one half gray and the other green. You can make a gray marbled effect by not mixing the dye in thoroughly. Wrap green fondant and reserved plain fondant separately in plastic wrap so it doesn't harden.
Roll out gray fondant onto non-stick surface. Cut and set aside several block shapes. Cut fondant into strips to fit the sides and top of cake. Using a dull knife, indent block shapes into fondant. Do not cut all the way through. Gently push the block strips onto the frosted cake. Using the plain fondant, dye it black and form to the birthday year number and set aside. Unwrap green fondant and shape into an outstretched hand.
Bend fingers to form fist. Using a dull knife, indent knuckles on fingers and thumbnail. Place fist on top of cake. One at a time, tuck the 4 licorice strips underneath cake, bend them, and push through fondant and into cake. Place reserved blocks on top of cake. Using gray frosting, pipe scallop edge on top and bottom of cake. Write verbiage on cake using green frosting. Place black fondant birthday number on cake board up against the cake.