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 :
DeVito played Martini in the 1975 film One Flew Over the Cuckoo's Nest, reprising his role from the 1971 off-Broadway play of the same name. He gained fame in 1978 playing Louie De Palma, the short but domineering dispatcher for the fictional Sunshine Cab Company, on the hit TV show Taxi.