Put 2 tablespoons of the frosting into a ziplock bag and snip off a corner. Use a few drops of red food coloring to tint the remaining frosting pink. Trim the top of the cake to make it level. Use our template (find it at familyfunmag.com) to cut the unicorn's pieces, then assemble them on a serving platter.
Warm fruit chews in the microwave for a few seconds to soften them. Knead together the yellow fruit chews and roll them into a 15-inch-long rope. Wind the rope around an 8-inch lollipop stick or a bamboo skewer to form the unicorn's horn. Flatten two of the pink fruit chews into disks and trim them into triangles to fit the center of each ear. Roll the remaining fruit chews into ropes. Set all the pieces aside.
Cover the cake with a layer of the pink frosting. Pipe two large dots of white frosting to form eyes and add a blue gum ball pupil to the center of each. Press on two pink gummy ring nostrils and the ear centers. Trim and arrange a marshmallow twist mane. Fill out the mane and form
the eyebrows with the remaining pink fruit chews. Add the candy horn right before serving.