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 :
This mammoth musical is at base the story of two sailors on leave in Hollywood. Brash Joseph Brady (Gene Kelly) has promised his shy pal Clarence Doolittle (Frank Sinatra) that he will introduce Clarence to all the glamorous movie starlets whom he allegedly knows so well. Actually, the only actress whom Joseph meets is bit player Susan Abbott (Kathryn Grayson).