My son wanted a Captain Underpants cake for his birthday. I actually found the idea from the coolest-birthday-cakes website and tweaked it a bit to work for us.
We made a 9 x 13 chocolate sheet cake and decorated it with homemade butter cream frosting. We made the frosting with 2 sticks butter, 4 cups powdered sugar, 1 tsp vanilla, and 3 T milk. We reserved about 1/4 cup of plain frosting for the teeth and underwear, and we dyed 1/2 cup of it light pink for the skin. We dyed the rest of the frosting blue. We also used some premade red and black frosting in a tube for the outlining and cape.
We printed out a coloring page image of Captain Underpants which we found via internet search (if you want to do an image with words, you will need to print out a mirror image of the picture). Then, I placed the coloring sheet on a hard wood board and covered it with a piece of waxed paper, which was taped in place. Then I used black tube frosting and a piping tip to trace the outline of the image. Then we piped in the white for the teeth and underwear, pink for the skin, red for the cape.
I covered the image with another sheet of wax paper and put the whole board in the freezer for an hour. Meanwhile, I frosted the cake with the blue frosting. After the butter cream image was completely hardened in the freezer, I removed it and slowly took off the top layer of wax paper. Then I flipped the butter cream image onto the cake. Then we SLOWLY peeled off the wax paper and smoothed over any rough spots on the image with a finger dipped in water. Then we just used a star tip to add a border and candy letters for the finishing touches.
Thank you to Amanda S. for giving me the idea! My son loved it!