My son loved Wheres Waldo books, and was thrilled when we found tablecloths and napkins.
The first thing I did for the cake was to enlarge a picture of Waldo. I then put wax paper over the enlarged picture and traced it with piping gel (bought at grocery store), using a small dot icing tip. I let this sit in the open to air for about 3 days so it would become dry.
I prepared a cake mix and, iced it white. I let the cake sit for several minutes to allow the top of the icing to become “hard” or no longer sticky to the touch. I then laid the piping gel picture face down on the cake and rubbed gently. Then I carefully peeled off the wax paper picture.
I was then able to fill in the Where’s Waldo picture with small icing tips just like coloring. The good thing about this technique is that it makes it possible to follow any theme!