Trim off bill and tail from 3-D Rubber Ducky cake.
Using a serrated knife, cut plastic dowel rod into 3 1/2 in. and 2 1/2 in. lengths. Insert 2 1/2 in. piece into center of chest area, angled up, with about 1 1/4 in. sticking out of cake. Insert the 3 1/2 in. piece into the head area, angled down, with the end resting on the smaller length.
Using buttercream icing and tip 8, cover dowel rods with icing. Pipe icing into end of dowel rod to cover end. Trunk will be covered with tip 18 stars when cake is decorated. Insert candle after piping stars.