1. Cut 1/2-inch triangles from corners of pound cake. (Save trianlges for another use, if desired.) Round edges of cake to resemble bun.
2. Cut cake in half horizontally, cutting almost all the way through but leaving cake halves attached. Place sliced cake on serving plate.
3. Cut 1/4 inch off both ends of one sponge cake; arrange in center of bun. Cut 1/4 inch off one end of remaining sponge cakes. Place, cut ends together, on either side of center sponge cake to resemble hot dog.
4. Spread frosting over hot dog, being careful to avoid bun. Squeeze yellow icing on hot dog to resemble mustard. Sprinkle diced gumdrops on hot dog to resemble relish, if desired.