you are going to need:
Sheets of "Fun Foam"
a Styrofoam ball (Ours was about 9 inches in diameter)
thick paper plates
an LED push-button light
a spinning stool-chair-thing
determine the size of your Styrofoam ball. you need to measure the circumference and diameter.
Make sure you have enough "Fun Foam" to fill the dimensions of [Circumference x diameter]
hot glue these pieces together so that it forms a sphere-ish shape (don't glue the last two together yet)
We researched from multiple sources, but this site proved the most helpful: http://www.turbosquid.com/3d-models/wheatley-video-character-robot-3d-model/602446
We used foam to cover most of the sphere. We also used it for various detailing elements.