Some day soon we may see little trash compacting robots like WALL-E here on Earth. Hopefully though the whole earth won't be a junkyard by that time!
Like most robots WALL-E is made up out of some basic geometric shapes. His body is a cube and his wheels are triangles with rounded edges. I've done a wavy line in black pencil for the wheels to make them look like treads.
The colours are transparent and applied with the paint bucket. I've done the finer details with pencil and used light grey pencil for highlights.
To make my WALL-E stand out, I've given him a pink background. With the airbrush, I merged light and dark pink with a midtone.