Whisk together powdered sugar, milk, cinnamon, and vanilla until fully combined. Place in fridge.
Make your favorite apple pie filling. Set aside.
Make your favorite pie dough.
Preheat oven to 375° F.
Roll pie dough to ¼-inch thick, if not thinner, on parchment-lined baking sheet.
Cut out apple shapes. Re-roll scraps and continue cutting shapes until out of dough.
Place up to 2 teaspoons of filling on half of the shapes. Be careful not to overfill.
Place lollipop stick on top of filling. Top filled shapes with unfilled shape. Crimp edges, especially around lollipop stick.
Brush each apple shape with beaten egg.
Bake for 12-15 minutes or until they're baked through. Remove apple pie pops from oven and let cool.
Transfer cinnamon icing to piping bag fitted with Wilton #1 or #2 piping tip.
Begin at edge of pie pop and pipe outline of skull, eyes, and nose. Fill in skull design with icing. Let icing set and enjoy!