I started with six 8-inch round cakes. I stacked four for the torso and shaped the remaining two for the head. Frosted with buttercream frosting.
I covered both pieces with white rolled fondant and painted R2's head with silver Pearl Dust. (This was the first time I've ever worked with Pearl Dust. I think I over-diluted it with lemon juice and it ran all over the place. To compensate, I added a little cornstarch, but that just made it gummy and gloppy. In the future, I will add less lemon juice or just use it dry. Pretty cool stuff though!)
R2's legs were blocks of rice crispie treats cut to shape...
...and covered with fondant.
Here's R2 stacked and getting some details with fondant tinted blue. (Please don't hate me, Star Wars fans; I know he'd not droidatomically correct! He ended up being shorter than I planned as the heavy fondant squished him down a bit. Oh well.)