Obvious stuntman of Robin as they climb the smokestack.
Batman and Robin escape the Joker's deathtrap by climbing back-to-back up the smokestack, using their bodies to keep each other from falling. However, when they reach the top, we see Batman climb completely over the edge of the smokestack's opening before we see Robin's hands take hold of the edge. What was he holding onto while Batman was finishing his escape?