The best advice I can give when making a Transformers Helmet Cake is come up with a clear plan and then put it together like a puzzle. You will want to be sure that you allow for adequate drying time before icing as there are quite a few cut surfaces. Also be sure to do a crumb coat before icing it and use smoothing techniques as you go along. I waited until the end to smooth it and by then the icing had dried and I was unable to smooth out the cake.
The eyes are actually made out of crushed up buttershop candies that were melted in the oven and then “snapped” to shape. The horns are made out of the wafer sandwich cookies that I sliced into layers, anything else is far to heavy.
I think next time I would do it with fondant.