This little droid is seen only twice during the special.  You once see him while he is with Luke, and you see him at the end, when the whole cast gets together and sings.  When you see him with Luke, he is only causing trouble.  He doesn't pay any attention to the X-Wing that they are reparing together.  And when you see him at the end, he says (C-3PO translates) that droids have feelings and emotions too. At a convention in Chicago in the summer of '99, Kenny Baker told the audience that he only played Artoo in the movies. So, the Artoo Detoo used in the Holiday Special isn't played by Kenny and is most likely remote controlled.