One to two days in advance: Make cookies. Prepare and roll out dough. Cut cookies using Lips Cutter. Bake and cool. Spatula ice inside of mouth with black icing; let dry one hour. Trace lips pattern with toothpick. Outline lips using full-strength icing and tip 3; flow in using thinned icing. Let dry 24 hours.
Cut white fondant teeth. Roll out fondant 1/16 in. thick. Cut a 1/2 in. wide strip; cut 1/2 in. squares for four top teeth. Cut a 3/8 in. wide strip; cut four bottom teeth 3/8 to 1/2 in. long. Cut two fangs, 3/4 in. wide at the top, 1 3/4 in. long. Attach using damp brush, trimming to fit curve of lips.