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 :
Kurtwood Smith. Kurtwood Larson Smith (born July 3, 1943) is an American television and film actor. He is known for playing Clarence Boddicker in RoboCop (1987) and Red Forman in That '70s Show, as well as for his many appearances in science fiction films and television programs (Star Trek, The X-Files).