Source: cinemablend.com
6. Emperor Joker
Hey, look, it's a Superman book crossover! One that ran through all of the Superbooks for a couple of months!
It opens with Superman waking up in Arkham Asylum, where he's been imprisoned for supposedly murdering Lex Luthor. He breaks out, but is apprehended by Earth's greatest hero, Bizarro. Needless to say, someone's been screwing with reality.
And that person was the Joker. Superman and Mr. Mxyzptlk (plus Steel, Supergirl, and Superboy) fight back against the suddenly all-powerful, reality-warping Joker. A Joker who has turned the rest of the Justice League into parodies of their former selves. Eventually, Superman defeats the Joker by pointing out that no matter what he does, he can't truly get rid of Batman, since the universe is spawned from Joker's mind, and he can't get Batman out of his head. And then they strip Joker's powers and have The Spectre break his mind.
Lasting Impact: Well, this crossover was adapted into a pretty good episode of Batman: The Brave and the Bold. Also, the Bizarro'd Justice League would see another take in the Geoff Johns Action Comics story about Bizarro.
