would anyone be able to tell me how I would be able to make this cake? what size cakes would I use and how would I get the head to stay up like that? thanks!!

http://www.cakecentral.com/g/i/1592930/a/1593930/3d-cake-covered-with-home-made-marzipan/

anyone?

I don't have much experience, but having done ALOT of reading, Maybe Rice Krispie treats for the head held on with straws or skewers? And then a carved cake body. Just a thought. Hope someone with more experience can help soon but thats what I would do.

This may help:   

It looks like 2 layers of 9 x 13 corners carved to make it more rounded.  The head can be RKT but if you need more cake you can bake in a half ball pan another cake.  The legs can be RKT or a mixture of cake / frosting just like for cake pops and then molded around the bottom cake.