To make the cake: Preheat the oven to 350 degrees F.
Butter and flour 1(6-inch) diameter and 1 (8-inch) diameter metal bowls. Combine the cake mix, coconut water, oil, and eggs in another large clean bowl. Beat for 2 minutes, or until well blended. Pour 2 cups of batter into the smaller buttered and floured bowl; pour remaining batter into the larger prepared bowl. Bake the smaller cake for 40 minutes and the larger cake for 45 minutes, or until a toothpick inserted into the center of the cakes comes out clean. Cool the cakes in the bowls on a cooling rack for 30 minutes. Invert the cakes onto the cooling rack and cool completely.
To decorate: Cut the larger cake in half, forming 2 half-moon pieces. Spread 1/4 cup of frosting over the flat top of each piece. Place the pieces cut side down on a work surface, adhering the frosted sides together. Trim 1-inch from 1 end of the cake; discard the trimmings. Repeat with the smaller cake. Place the larger cake on a serving platter. Spread 2 tablespoons of frosting over the trimmed end of the smaller cake. Place the trimmed end of the smaller cake against the trimmed end of the larger cake. Spread the remaining frosting over the cakes to cover completely. Sprinkle with all but 1/2 cup of the coconut, pressing to adhere. Brush the melted milk chocolate over both sides of the chocolate chunk cookie halves to coat completely. Sprinkle with the reserved 1/2 cup of coconut; set aside until dry. Press 2 semi-sweet chocolate morsels onto the bunny face for eyes. Using a toothpick, secure the gum drop onto the bunny face for the nose. Using toothpicks, secure the licorice pieces onto the bunny face for the whiskers. Using toothpicks, secure the mini-marshmallows onto the bunny face for the teeth. Make 2-inch-deep cuts atop the bunny head; insert the chocolate cookie halves for ears. Roll large the marshmallows together and secure with a toothpick onto the bunny for a tail.