Prepare the brownie mix according to the package directions.
Pour the batter into the silicone brownie pops pan and follow the pan instructions for filling, inserting the sticks, and baking. Let the brownie pops cool completely.
Make the fondant by placing the marshmallows in a large microwave-safe bowl with 2 tablespoons water. Microwave for 20 seconds, stir, and continue in 20-second intervals until completely melted.
Add 1½ pounds of the sifted confectioners' sugar to the melted marshmallows and begin mixing. Grease your hands and work surface with vegetable shortening, then knead in more confectioners' sugar until the fondant forms a smooth, elastic ball.
If the fondant feels tough or tears easily, work in additional shortening until it becomes smooth and pliable. Coat the surface lightly with shortening, wrap tightly in plastic wrap, place in a resealable bag, and let rest overnight.
When ready to decorate, keep the unused fondant wrapped while working. Roll a portion to about ⅛ inch thick and cut out large circles. Smooth the edges with your fingers if needed.
Place the brownie pops on a piece of Styrofoam for support. Dab a little water over the top of each brownie pop, then drape a fondant circle over it.
Arrange the fondant folds around each brownie to create a flowing ghost shape. Allow the ghosts to dry for a few hours before serving.