Source of a Joker Quote?

"Give a man a mask and he will show you his true face" Has been attributed to the Joker, but from what I've found, it is a derivative of a quotation of Oscar Wilde "Man is least himself when he talks in his own person. Give him a mask, and he will tell you the truth."

However, there seems to be a lot of folks who claim that the alternative form was indeed uttered by the Joker. I'd like to know what was the context of this quote. Specifically, what issue, or movie, or episode it can be found in.

Thanks!