1974 Mego DC Comics Super-Foes 8-Inch Action Figures
In 1974, Mego released their Super-Foes series of action figures which was, of course, part of their successful 8" World's Greatest Super-Heroes line of DC and Marvel comics superheroes and – now – villains.
The Mego Super-Foes series included the Batman & Robin villains Joker, Penguin, and Riddler, as well as the Superman villain Mr. Mxyzptlk.
It's a little strange that Mego chose Mr. Mxyzptlk over Superman's main nemesis Lex Luthor. Perhaps they wanted to get more use out of the fat-man body which had been created for use on their 8" Penguin action figure even though Mxyzptlk wasn't at all fat in Superman comic books from DC.