During the scene which begins this second parter, in which Batman and Robin are in the process of being spun to death on the Riddler's giant machinery wheels, "Robin" can clearly be seen to be a life-sized stuffed rag doll; the stuffing in "his" legs shifts progressively towards the center of the wheel.
When Batman hurls the Riddler's orange-clad henchman through the air during the fight, the wires holding the henchman aloft can be seen.