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 :
In Curtain: Poirotâs Last Case, Poirot (David Suchet) and Captain Hastings (Hugh Fraser) are together again for the first time since 2001 where they will return to Styles Court, the scene of their first case together, where Poirot declares that one of the guests is in fact a serial killer.