i also had a few inquires about how i made R2, so i hope this post can be of some use.
here are a few sketches + schematics form last year's R2D2 costume. i decided on a soft construction early on. i wanted my nephew to be comfortable + have ample mobility. i also decided to forget about R2's arms + just concentrate on his iconic garbage can physique.
from that point on, i worked primarily from a couple R2 toys on loan for reference. the entire costume is made from only a few simple sewing materials: fabric [white corduroy, silver lame, blue felt + blue satin], thread, batting, boning + velcro.
click on photos for larger view.
the headpiece has three strips of boning inside criss-crossing each other for structure [like drawn above]. there is a third strip of boning along the botton edge, as well as velcro pieces [to attach it to the body]. i used a beach ball to help draft the pattern + provide proper curvature. after he wore it once, a soft pillow was attached inside on top for extra comfort. the bones inside the top became uncomfortable after too much dancing.
all the detailing in the body is either quilting or applique.
the two ends velcro together + the head velcros to the body.
the two slits are little boy arm-holes for ample candy grabbing.
more costume pics may be found here.