Get two cardboard boxes, one slightly bigger than the other, and spray-paint them silver. In the bigger box, cut a hole for the wearer's head to go through. Remove the bottom of the other box and cut it to fit the wearer's face. Bend the bottom outward and attach it to the larger box.
I couldn't decide what to put here. I thought of making this part magnetic and sticking toy gears on it. Another idea was to put my iPod Touch here and run a cool app. In the end, I decided on this instead. What's in it?
This satellite dish is made by painting a plastic bowl and then attaching it to a small motor. A switch turns it on and off. The head is attached to the robot body using velcro just in case you don't want to wear it. I considered making a slot to put "Brain Candy" in, but that would make the costume too heavy and creep my son out. Another idea was to have a bubble blower on top, but that might have been messy.
Some robot arms and legs inspired by Made by Joel. The decorations are attached using velcro and can be moved around. The elastic in the back goes around the wearer's arms and legs. It's a good idea to make a robot shirt to go with these so that your child can wear the shirt with the arms and legs as a costume when the whole box costume is too awesome (and uncomfortable) to wear for an extended time.