Our R2D2 Birthday Cake Design isn't particularly unique, but it turned out well and I have some tips to pass on that were not shared for the R2D2 cakes already shown.
We used four 9 in round layers plus a 9 inch dome top and a Styrofoam base. Rice Krispy treats worked well for the arms.
1. Plan on the dome top taking nearly an hour to bake, despite the instructions on the 9 in ½ dome pan saying 30 minutes. 2. Frosting a Styrofoam base will give you the height without the weight ? or wasted cake. 3. We put cardboard rounds between the 2 sets if 2 layer cakes and under the dome for ease in slicing the cake. However, we learned that 9 inch cardboard rounds stick out from cakes baked in 9 in cake pans. We had to cut ours down to 8 inches or less. 4. A dowel down the center for stability is essential especially if you drive the cake to a party venue. I didn't know what it meant to "dowel" a cake so I'm going to tell others who may be as ignorant as I was.
This means you go to the hardware store and get about ½ or ¾ inch dowel, which then has to be cut to size because they are pretty long. You can sharpen them in a pencil sharpener for easier insertion. But don't believe anyone who tells you it is possible to push a sharpened dowel through the cardboard as well as the cake. We carefully marked the exact center and used a drill to make a hole through all 3 cardboard rounds a little larger than the dowel for ease of insertion.
It is probably essential to use pieces of the dowel to stick the arms into the body of the cake too. You can also put small dowel pieces in the layer cakes to keep them together. 5. Make sure your Rice Krispy treats are totally cooled, maybe even frozen when you carve and attach them. Press them down hard when you put them into the pan in order to make them dense and strong. 6. Colored fondant is the easiest way to decorate, but candy stores offer some cool "button" ideas.