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 :
PG | 1h 29min | Animation, Adventure, Comedy | 31 March 2000 (USA) Two swindlers get their hands on a map to the fabled city of gold, El Dorado. Bibo Bergeron (as Eric 'Bibo' Bergeron), Don Paul | 1 more credit Â». Terry Rossio (screenplay), Ted Elliott (screenplay) | 1 more credit Â». Kevin Kline, Kenneth Branagh, Rosie Perez | See full cast & crew Â».