Decorate cake ball pops. Prepare buttercream icing following recipe directions. Tint black. Use tip 3 and black icing to pipe a large dot of icing on back of one large eyeball. Position on cake ball pop, and push so that icing oozes out of sides. Repeat for small candy eyeball. Use tip 3 and black icing to also pipe string mouth.
Attach hat. Use melted white candy in cut disposable decorating bag to position and attach hat to top of pop.
Use scissors to cut pipe cleaner to 5 in. long and wrap around lollipop stick.