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 :
During the same year Star Wars: Episode V - The Empire Strikes Back (1980) was released, R2-D2 and C-3PO appeared in 2 episodes of Sesame Street (1969) Season 11, as well as in an episode dedicated to Star Wars in The Muppet Show (1976), alongside Luke Skywalker (Mark Hamill) and Chewbacca in the latter.