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 :
Wayne Rogers who played beloved character Trapper John McIntyre on hit show M.A.S.H. dies aged 82 in Los Angeles. By Associated Press and Paul Chavez For Dailymail.com. Published: 21:33 EST, 31 December 2015 | Updated: 03:12 EST, 1 January 2016. 3.2k shares.