In 1980 Alberca et al. described a patient with a syndrome of increased muscle irritability, who presented ondulating muscle rolling movements and electrically silent cramps, myoedema and muscle reactions to mechanical stimulation similar to myotonic response, suggesting a disfunction at myofibrillar level.
For c-3po, it was a costume, Anthony Daniels played c-3po: For R2-D2, It was a costume and a remote controlled robot. CGI was also used in the prequel trilogy. So, they had Kenny Baker to play him : And from Portrayal section of wookieepedia article on R2-D2 :
In theater, Goodman played the Ghost of Christmas Present in the 2008 Kodak Theatre production of A Christmas Carol, starring Christopher Lloyd as Ebenezer Scrooge. He played the role of Pozzo in a Studio 54 revival of Samuel Beckett's play Waiting for Godot, opposite Bill Irwin and Nathan Lane. John Heilpern of Vanity Fair called it the greatest Pozzo I've ever seen.