"Surf's Up! Joker's Under!"
After being stuck with poisonous sea urchin spines, Batman and Robin are tied down to workbenches, and Joker explains to them the process by which they are about to be turned into surfboards.
Coated in hardened foam, Batman and Robin are helpless. As Joker's men start to apply the catalyzed rosin to the foam blanks, Batman activates the portable ultra-violet bat-ray on his utility belt. The highly combustible rosin then explodes violently, releasing Batman and Robin. Luckily, the foam dissolved the sea urchins spines, along with their poison.
Joker believes an army full of sunburnt teenagers is the key to taking over Gotham City.