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 :
Tony Dow was born on April 13, 1945 in Hollywood, Los Angeles, California, USA as Tony Lee Dow. He is an actor and director, known for Leave It to Beaver (1957), The New Leave It to Beaver (1983) and General Hospital (1963). He has been married to Lauren Shulkind since June 16, 1980. They have one child.