How to Make It
Crumble the cake into a food processor. Add the butter, lemon zest, lemon juice and sugar and pulse to combine. Transfer the mixture to a bowl and shape into 18 mounds. Gently press them into ghost shapes and ease each one onto a popsicle stick. Stand the pops upright in a large piece of Styrofoam.
In a large microwave-safe bowl, heat the white chocolate at high power until three-quarters melted. Stir until completely melted and cooled to 88° on an instant-read thermometer. Working quickly, dip the cake pops into the white chocolate, letting any excess drip back into the bowl. Stand the pops upright in the Styrofoam and let the chocolate set. Use the edible decorating pen to draw faces on the ghosts and serve.
Popsicle sticks and edible decorating pens are available at baking supply stores.