In advance: Mold candy skulls. Attach halves together with melted candy.
Also in advance: Make arms. Dip pretzels in melted candy; set on waxed paper-covered board. Chill until firm. Trim pretzel to 2 1/2 in. long. Attach pick to pretzel stick with candy; let set. Using melted candy in cut parchment bag, pipe hand, fingers and thumb around stick. Chill until firm.
Bake and cool cupcakes. Ice smooth with chocolate buttercream tinted black and immediately cover with black
sugar. Position candy skulls. Insert arms.