With a channel cut through the Coroplast, it can be folded..
...like this, allowing all kinds of complex shapes.
While the exterior is Coroplast, the interior uses a skeleton of PVC to support the structure along with providing pivot points at all the joints and connections at the stilts. All the individual pieces are bent, butted up together around the skeleton, then fastened using high-temp hot glue.
The main frame of the body which would support the backpack frame and massive head were made from .063 Aluminum sheet.
(Above is a PVC shopping list I found when I visited Scott's shop.)
I began building detail pieces. Rigid pink insulation foam sheets from Home depot were easily cut into intricate patterns on a scroll saw. Hot glue and sanding shaped the pieces into guns and trim pieces.