Make jack-o?-lantern topper one week in advance. Knead 1/8 teaspoon Gum-Tex into 2 oz. of fondant. Tint fondant orange. Use 9 in. fondant roller with purple guide rings to roll out orange fondant 1/8 in. thick. Use pumpkin cutter from set to cut one shape for each treat. Let dry on cornstarch-dusted board.
Prepare buttercream icing following recipe directions. Tint portions black, green and violet. Use tip 1 and black icing to pipe in eyes, nose and zigzag mouth. Reserve remaining icing.
Make cupcakes. Prepare batter following recipe directions. Bake and cool cupcakes.
Decorate cupcakes. Use tip 2A and green icing to pipe ring around edge of cupcake. Use tip 32 and violet icing to pipe swirl in center of cupcake. Position jack-o?-lantern sprinkles around edge of cupcake. Insert topper.