Step 1: Bake the chocolate cake according to the package directions and allow it to cool completely.
Step 2: Crumble the cooled cake into a large bowl until no large chunks remain.
Step 3: Add the frosting to the crumbs and mix with a spatula or your hands until a dough-like consistency forms.
Step 4: Roll the mixture into 24 even balls (about 1.5 inches each) and place them on a parchment-lined baking sheet.
Step 5: Refrigerate the cake balls for at least 2 hours or freeze for 30 minutes to firm up.
Step 6: Melt the green candy melts in a microwave-safe bowl in 30-second increments, stirring until smooth.
Step 7: Dip the end of a lollipop stick into the melted candy, then insert it halfway into a chilled cake ball.
Step 8: Submerge the entire cake ball into the green coating, tap off the excess, and insert pretzel pieces into the sides for bolts before the coating sets.
Step 9: Once the green coating is hard, melt the dark chocolate and dip the top of the pop to create hair. Use a toothpick to draw a face and stitches.