Lex Joker ain't even original! There was a Lex Luthor/Joker mash-up in the Elseworlds one-shot, Superman: Speeding Bullets. Standard issue "What if Kal-El's rocket was discovered by Thomas and Martha Wayne instead of Jonathan and Martha Kent?" situation. In this version, he uses his powers as Batman, while Lex Luthor ends up in a chemical accident that turns him into the Joker. Oh, and Lois ends up falling for Bruce Wayne while deploring Batman's strongarm tactics. Whatever. Eduardo Barretto's art was good though.