I made the WALL-E cake for the robotics team end of year party. It was a big hit. Only the orange box is cake, all the rest is inedible materials that I added for effect. I removed it before serving.
In advance, make the arms, wheel units, shoe and head/eyes out of Styrofoam. Cover with rolled fondant, using picture or photo above as a guide. Find a piece of pliable black metal to use as the neck/head support. We used a left over shelf support - my husband used his manliness to bend it as pictured. (I really have no clue what he did, but it was perfect!)
Also in advance, make the fondant decorations for the front of the cake. (buttons, control panel, and the "E" in a red circle)
1. You need a square block of cake. Using a 10" square pan, this means you need 5 2" layers. Bake all the cakes and let cool. If you use an 8" pan, you'll need 4 2" layers.
2. Level the cooled cakes. Do not skip this - if the cakes aren't level, your cake will be crooked and unstable. See: http://www.wilton.com/cakes/making-cakes/leveling-cakes.cfm
3. Using square cake "rounds" (cardboard separators), make 1 2 layer cake and 1 3 layer cake, with buttercream icing between the layers. I had to cut the separates from larger rectangular ones as my store didn't have square "rounds" in stock in the 10" size.
4. Stack the 2 cakes on your cake board, using dowels to support the top cake. (I used a plastic 10" cake stand that had little feet - nice to get the cake off the board so it looked right with the wheel units.) Do not skip the dowels! Your cake cannot stand without dowels! See: http://www.make-fabulous-cakes.com/tiered-cakes.html
5. Frost the entire cake smooth with orange tinted buttercream.
6. Using a can of red or brown edible spray color, spritz the cake unevenly to make it look worn. Just a few sprays, being careful to not overspray. Then add the fondant decorations. Pipe gray stripes on edges using a large round tip, such as a Wilton No. 5. Pipe the "WALL" using a No. 3 tip in black.
7. Insert the black metal neck rod, with the head attached. Using skewers, insert the arms. Note - the stripes on the arms should be on the side. I attached them wrong, but didn't notice until much later. Position the wheel units with skewers as well. Set the shoe in front, adding a bit of Oreo cookie crumbs for "dirt" and an bit of plant. (I used some spinach leaves. I didn't have Oreo crumbs, so I used graham cracker crumbs, Oreo would have been better.)
This is why I make cakes: