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 :
Kenny Baker, the actor who played R2-D2 in Star Wars, died Aug. 13 at age 83. Baker played the famous droid in the original and prequel Star Wars trilogies. Ironically, he had an acrimonious relationship with Anthony Daniels, who played R2's beloved companion, C-3PO.