My younger son will be two in December. He loves R2D2, whom he calls "R2 2D." Close enough.
The costume is white fleece with colored fleece and sewn details. The arms attach to the shoulder with a tab of Velcro, and then some elastic (held together with a toggle) keeps the arm attached around his forearm. We live in Minnesota, so it has to be wearable for a variety of weather -- either over a T-shirt or over a snowsuit.
The hat is some stretchy silver material that wasn't as hard to sew as I thought it was going to be. (Phew!) But by the time I got to the hat, I was sort of done. So all the details are just hot-glued on. (Sort of humiliating, but a person can't stay up drinking wine and making costumes all night long ... at some point, she hast to sleep. Right ...?)
Thanks for looking!