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 :
Frank Thornton as Captain Peacock (with the moustache in the second row from the back), Nicholas Smith, Wendy Richard, Arthur Brough, John Inman, Mollie Sugden and Trevor Bannister. Nicholas Smith, 79 â who played Mr Rumbold â is now the only surviving member of the original main cast.