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 :
Larry Stewart with one of the horses used to portray Triple Crown winner Secretariat in the Disney movie of the same name. The two leading stars of the film, Diane Lane, who plays Secretariatâs owner, Penny Chenery, and John Malkovich, who plays trainer Lucien Laurie, were at the track. So were the filmâs director, Randall Wallace, and one of the producers, Mark Ciardi, and several others involved in the production.