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 :
John Mahoney (born 20 June 1940) is an English-born American actor. Born in Blackpool in North West England, Mahoney started his career on the stage in 1977 as the body double for Steve McQueen and moved into film in 1980. He played Martin Crane in the American sitcom Frasier on NBC from 1993 to 2004.