An oldie but a goodie ... and still the Joker's favorite way to get gum off his shoe. Apparently, he's already managed to kick the Bat-logo off Batman's chest.
The Joker's quite limber, isn't he? Must be those yoga classes at Arkham.
Try that maneuver sometime with a friend and see how many tries it takes to send him flying over the bannister or simply snap his spinal cord.