Frost cupcakes and set aside. Lightly dust work surface with cornstarch and roll fondant a little thinner than ⅛ inch. Cut 18 1½-inch rounds and 18 4-inch rounds with cookie cutters. Knead scraps together and reroll, as necessary.
Insert the stick of a lollipop into a block of Styrofoam (or half a potato or apple) to hold it steady. Place one 1½-inch fondant round over lollipop and pinch to close. Then place larger fondant round over the smaller one, pleating to make a ghost shape. Repeat for all lollipops. Place a ghost in the center of each cupcake by inserting the stick into the cake. Pipe black eyes on each.
Fondant scraps can be re-rolled. Imagine the fun your little ghosts can have!