I thought about making this post a How To's-day post, but I don't think I'm qualified to tell you how to make/decorate a caterpillar cake of your own. I'll just share how I made my cakes, and if you're at all cake-decorating-inclined, you'll be able to figure it out from there.
So for starters, the planning for this cake started in May, when Baby E's momma approached me with the theme for his first birthday party. The theme? The Very Hungry Caterpillar, the children's book by Eric Carle. I immediately thought a cake with the food items the hungry caterpillar ate placed on the border would be adorable. That day, I sketched a cake in MS Paint to share (click to enlarge).
So for starters, this is a lot of cake. Baby E's momma told me to plan for 25 adults and 15 children (Baby E is pretty seriously loved). Because of the fondant food pieces on the side of the cake, I knew I wanted to make a double layer cake, and I knew I wanted to make it half-chocolate/half-yellow cake to satisfy both preferences. To make it a little easier on me, I baked two 9x13 cakes in each flavor (rather than making a half-sheet cake in each flavor, then cutting each in half to stack),then I basically placed my two layer cakes right next to each other to make my two-layer half-sheet cake.
I frosted the cake with vanilla buttercream, and I am thrilled to report that I've finally figured out the correct timing for maximum whippy-ness in my frosting. Roughly five minutes in the stand mixer with just shortening, water and vanilla, then another five to seven minutes with the powdered sugar added is about perfect! (2 cups shortening, 2 tsp vanilla, 1/4 cup water, and just short of two pounds sugar) I think it took three batches to frost the cake (including filling), fill and frost the smash cake, and do the decorating on both. I also used some of this frosting to make the oversized cake pops that make up the caterpillar on top of the main cake. Those were not terribly successfully, and I think it had something to do with my extra-whippy homemade frosting.
To make the food pieces around the sides of the main cake, I feel like I kind of cheated. First, I purchased Wilton's pre-colored fondant so that I'd at least have primary colors to get started. The pictures in the book are beautiful and textural, so I knew I'd want to blend colors in a choppy way, and starting with pre-mixed primary colors helped me do that. Second, I used the book itself as my guide, rather than free-handing each shape. I scanned the pages that show the fruit into MS Paint and outlined each shape. Then, I deleted the the color and printed out outlines (I'm sure there is an easier way to do this, but this worked for me). I sized the shapes as a group so that they would retain their scale and made the largest pieces just shorter than the height of the cake. Then, I cut out each piece from my printout (cutting shapes apart for different colors as needed) and then placed each stencil on top of a rolled out piece of fondant to cut around.
When it was time to put the cake together, I cut out the hole the caterpillar went through and pasted the shape onto my cake using a liquid glue made of gumpaste and water. I waited to cut out the holes so I could intentionally put them in different places. This was one of the few times I went totally off-script and didn't always place the holes where they were in the book. After I'd put all of the pieces on the sides, I went back and hollowed out the hole area with a toothpick. This way, you could see all the way down the hole to the cake, and it looked like the caterpillar was eating his way through. (It was also a pretty useful way to see which half of the cake was the chocolate half and which was yellow!)
I mentioned above that the caterpillar on top was made of oversized cake pops (Go here to see what the heck a Cake Pop is and how to make your own). A. You probably should not try to make them twice as big as recommended. B. Use store bought frosting, or add a lot of extra sugar to your frosting to make it much stiffer before making your cake pops. C. You might ought to let your cake dry out a bit. Mine was fabulously moist, which probably didn't help the cake pop. Just my thoughts. I basically had to keep mine frozen until just before the party, and I had to give up on the 'pop' idea. The melted chocolate and frosting mess pretty much had to be shoveled off the cake before slicing (but it looked good on the cake, and isn't that what counts?).
To cover the cake pops, I put the frosting in a glass and rolled the ball around in it. Then, I used a knife to tap the frosting and make it stand up like the hairs on the caterpillar's back. I formed the antennae out of an extra cake pop that I didn't think I needed on the cake.
The smash cake almost felt like an afterthought because it was so easy to make, compared to the detail-oriented main cake. I think the idea of a caterpillar (at least, green worm) eating through an apple isn't specific to this book, but you don't often see a caterpillar on an orange, so I did that for the smash cake. This was just a double layer 6-inch round cake that I shaped a bit at the top to make it a little more orange-shaped. After the frosting set a bit, I went back and added dimples all over.
So there you have it, my take on The Very Hungry Caterpillar, in cake form!