I used a recipe for a chocolate-marble-cake and scaled it up as I needed to bake 3 cakes for the Hungry Caterpillar 1st Birthday Cake.
2 x 25cm bundt cake rings 1 x 15cm round cake tin (you could use a 10cm one, I just had a 15cm one so had to cut a bit more off).
I mixed the batter for the next cake as the previous cake was cooking to keep the batter fresh and results consistent, washing, drying and regreasing and reflouring the cake tins inbetween. For the round tin, I made the quantities ¾ of the original recipe (3, not 4 eggs, etc) but even this made a little too much batter, so I got a few cupcakes out of it. I greased the tins with butter on a piece of kitchen paper and used a cocoa shaker with a mix of cocoa powder and flour to coat the entire tin well, makes sure the cake comes out NO PROBLEM! Then when all cooled on wire stands, I cut the cakes to size (see pic 2)
I couldn't find a cake board big enough (I ordered one, too small) so I ended up wrapping the packaging that my cake board had come in (with cake board inside for added strength!) with the reverse of some wrapping paper I had (so you could see the white side), and typed out "The Very Hungry Birthday Boy is (my son's name)" in the style of the front of the book. The typeface is Bodoni Regular. I then got a piece of glass cut to size (in this case, 66x52cm) by my local glaziers to make a cake-proof book cover and slipped the cut-out type beneath it in place!
I used buttercream icing with a LOT of green food colouring for the green, almost a whole bottle of colouring for one tub of icing! I was getting concerned about the amount needing to go in, so at some point I stopped adding and decided to paint the colouring onto the surface to get it more intense in parts, with a thick paintbrush, to get that painterly quality Eric Carle's illustrations have. I painted in a bit of yellow and blue food colouring in places too, to get a variety of greens.
The pieces, I stuck together with more of the coloured icing between each piece. Ditto the red face. I got it to a strong pink, then painted neat red colouring on top. I made the features (eyes, nose, antennae and feet) with more buttercream icing and sifted icing sugar into the paste to make it thicker and like plasticine, adding food colouring along the way and adding more icing sugar. For the feet, I didn't have brown food colouring and was trying to mix it, then hit on the genius idea of using cocoa powder to get the right colour! I rolled the coloured thick icing out to 2-3mm thick and used a knife to cut the shapes out. The yellow parts of the eyes just set into the buttercream icing, the green bits on top I stuck with a little more buttercream icing as "glue". Ditto the antennae. The feet I just moulded with my fingers and placed on the board.
Lastly, I made a slightly runnier paste of buttercream icing and yellow food colouring and put in a squeezy icing bottle, to run a "ribbon" of icing along the caterpillar's "spine" all the way along. I then got a teaspoon and carefully spooned "hundreds and thousands" along the spine so they stuck into the wet yellow icing too represent the coloured fuzz on his back.
I didn't want to ruin the look by plonking a huge candle into my caterpillar, then hit upon the idea of using a tealight holder that I already had for the "sun".
Lastly, I themed all the rest of the food round the foods the caterpillar ate, slices of apple, pear, oranges and plums (arranged to make "suns")...bowls of strawberries, salami (on the pepperoni pizza), party sausages, mini cupcakes (which I shop-bought, then iced in the colours of the dots in the book with left-over icing), mini cherry bakewell tarts (for the cherry pies), pickled gherkins, Babybel Swiss cheese, Smarties ice-cream cones, and I even sourced those swirly retro lollies online! I themed the goodie bags around the same with Caterpillar stickers, bubbles and balloons plus freeze-dried strawberry snacks and real-fruit orange chews. For the older kids I added a swirly lolly and little bracelets (just for fun and colour).