Father! The Earth is Near!! (Chichi yo! Chikyuu wa Chikai!!- 父よ!地球は近い!!) - S1.E18

Dr. Gou and some slaves managed to escape to earth but they were attacked by Zuuru and Gou was held in Sky Rook. Zuuru used him as hostage but Voltes team didn't believe he was the real Dr. Gou as they had been tricked many times and thought he was just another dummy robot (see episode #15). Things got complicated when Kenichi spotted tears in the suspectedly Dr. Gou dummy robot just before he was going to slash Sky Rook with Tenku-ken. What robot can shed tears?