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 :
Clarabell the Clown. Clarabell the Clown was the mute partner of Howdy Doody. Three actors played Clarabell. The first was Bob Keeshan, who later became Captain Kangaroo. Keeshan was succeeded by Robert Nick Nicholson, who also played the character of J. Cornelius Cobb on The Howdy Doody Show.