Preheat oven to 375 degrees. Line a cupcake baking sheet with paper liners.
In a medium bowl, whisk together the flour, cocoa, baking soda and salt until combined. Set aside.
Using a stand mixer, cream butter and sugar until light and fluffy. Add eggs, one at a time, beating well after each. Add vanilla.
Add chocolate PB milk and coffee to mixer. blend slightly. Add dry ingredients last and blend well, about 2 minutes.
Pour batter into baking cups about 2/3 full.
Bake for 15-20 minutes or until a toothpick inserted in the center removes cleanly. Remove from oven and let cool completely.
To make skeletons, heat white chocolate chips and egg nog in a microwave safe bowl for 30 seconds. Stir until blended.
Dip mini pretzels in white chocolate and place on wax paper to cool.
Insert a marshmallow into the end of a cake pop stick. Insert 3 chocolate covered pretzels below marshmallow to make the body. Draw faces onto marshmallow heads using black gel icing. Insert finished skeletons into cupcakes. Serve and enjoy!