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 :
As previously announced, Javier MuÃ±oz, who alternated in the title role of Alexander Hamilton with writer-star Lin-Manuel Miranda, assumes the role full time July 11. Miranda, Tony winner Leslie Odom, Jr. and Tony nominee Phillipa Soo play their final performances July 9.