For the puffed rice marshmallow treats: Melt the butter over low heat in a large saucepan. Add the marshmallows and stir until melted. Fold in the puffed rice cereal. Press the mixture into a large baking pan using a buttered spatula.
For the red velvet cake: Preheat the oven to 350 degrees F.
In the bowl of a stand mixer fitted with a whisk attachment, cream together the shortening, sugar and eggs. Next add the baking soda, cocoa powder, salt, vanilla, vinegar, food coloring and buttermilk, and begin mixing on low speed. Gradually add in the cake flour and continue mixing until the ingredients are well combined. Pour the batter into a greased, football-shaped cake pan. Bake until a cake tester comes out clean, 30 minutes. Let cool on a cooling rack, then invert the cake from the pan.
For the cream cheese buttercream: In a stand mixer, beat the butter until light and fluffy. Add the cream cheese and vanilla, and beat until fluffy. Gradually add the sugar, beating until incorporated and fluffy.
Frost the top (the domed side) of the entire cake. Cut out and use the marshmallow treats to form the head, tail and feet of the armadillo. Attach black licorice rope vines to make the eyes and tail.