The Superman Who Laughs
In order to trick the Batman Who Laughs, Superman decided to go undercover. If he really did infect himself with the Joker venom to turn into the Superman Who Laughs, I don’t know. Seems risky though if he did. Maybe a lesser or weaker dose of the venom so he can still maintain his mental faculties? I doubt Batman would go along with a full dose. Or maybe Clark’s just acting with some really good makeup on.
From – Batman / Superman Vol. 2 #2