R2-D2 (called R2, or "Artoo"), Luke Skywalker's trusty astromech droid and colleague of C-3PO, is the only character (despite being a non-living droid) to appear in all six Star Wars films, without changes to appearance or speech. R2 is barrel-like in shape, with a rotating dome which functions as his head, complete with a single robotic eye, a comparison to a pedal operated rubbish bin can hardly be avoided!