10 Mind-Blowing Facts You Didn't Know About Justice League Unlimited
3. Smallville's Lex Luthor (Briefly) Plays Lex Luthor
The episode of the Justice League where Lex Luthor and the Flash briefly swap bodies is infamous among comic fans and cartoon lovers alike, largely for the hilarious moment where Luthor tries to reveal Flash's secret identity, only to realise he has no idea who the face beneath the mask actually belongs to.
Better yet, when the pair swap minds, they don't trade voice actors, meaning that the voice of the Flash, Michael Rosenbaum, would briefly voice Luthor while he was in the speedster's body.
The beauty of this is that Rosenbaum also was at this point playing Lex Luthor in the live-action television show Smallville, which had begun five years later. This meant that, for one glorious episode, Rosenbaum was both the live-action face and cartoon voice of Superman's arch-rival, like some bizarre patron saint of bald villainy.