From the cliffhanger to the Impractical Joker / The Joker's Provokers pair of episodes of Batman. The Joker locks Robin in a wax spray booth and turns him into a wax figure.
“First, a wax spray job, somewhat similar to what you get when you have the Batmobile washed. It takes a week or so for the wax to harden properly.
"Start with a light spray. When every pore in his body is filled with wax, we'll apply a heavier coating.”