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 :
Guillaume was best known for playing the wry, sharp-tongued Benson DuBois, first as a supporting player on the primetime soap opera parody Soap (1977-81) and later as the star of the ABC spin-off series Benson (1979-86), in which his character rose from butler to lieutenant governor.