My son saw the cake done by "cookiecutters" (http://www.cakecentral.com/cake-photo_1889243.html) and immediately decided that was what he wanted for his 4th birthday. I took some inspiration from it, and made a few tweaks here and there. It worked in my favor that the rough "sketch-y ness" of the black royal icing detail lent itself to making it look even more cartoony.