My son had to bring a decorated cake to his recent scouts pack meeting for a cake contest. We scoured pinterest for ideas and he decided on an R2D2 cake. I used this cake as an example and changed it a little as I went. I made two cake mixes and used about 2/3-3/4 of it. I made an 8" round and an 8" square and filled them up so they'd be thick. You could probably get away with using just one mix and making them thinner. I cut all the pieces like so, and brushed on a layer of simple syrup. The legs are cut from the sides of the square cake. The circle is cut in half, one part used for the head (trimmed to the width of the body) and the other half cut into the 3 "feet". I also shaved part of the top sides of the body to give it a more rounded effect.
Then I did a crumb coat. I highly recommend a crumb coat, especially if you have cut the cake into different pieces as the cut sides get very crumby very fast. Then your frosting is all crumby and not very smooth-like. For the crumb coat just use a very thin layer of frosting, it will get crumbs in it but that's ok, then refrigerate the cake until it's firm. I used this buttercream frosting recipe but added a 1/2 cup-1 cup more powdered sugar. It was kind of too thick to use for the crumb coat so I added several more tablespoons of heavy cream and several tablespoons of milk to thin it out a little.
Then I did the final layer of frosting. After getting all the frosting on it, I used a wide knife (a frosting spatula would work better but I didn't have one) dipped in hot water to go back over the frosting to smooth it all out. The heat of the metal melts the frosting just enough to get it extra smooth. It's not fondant smooth, but smoother for decorating. Then my son and husband took over to finish decorating the cake. (Ok, it was supposed to be a father-son activity but I got it all done while they were at work-school and saved the best part for them.)
They used this picture as a guide. (I also came and helped smooth out some of their piping globs.)
I think the final cake turned out great, especially since an 8 year old was doing the decorating and I'm not a big cake making person. Zach was super excited about it. He didn't win a prize, but got a certificate for the most inter-galactically bad to the bone cake. My husband told him that meant "space cool".