I really like what they did with the sometimes trite "brain switch" plot in this episode. It's great to hear Michael Rosenbaum play Lex Luther trapped in Flash's body since he plays Lex on Smallville. But Clancy Brown captures Rosenbaum's characterization of Flash perfectly. I TiVo'd this episode and watched it twice, each time forgetting that it wasn't Rosenbaum voicing Lex. He gets the inflection and cluelessness of the character while he's trying desperately to not be discovered as an impostor so down it's unbelievable.
Best line of the show happens in the Mens Room in the Secret Society of Super Villains HQ after FlashLex tries to call the Justice League on Lex's Cell phone and is called out of the stall by Dr. Polaris to go to the big meeting to discuss Lex's plans for a huge heist:
Dr. Polaris: "Wait. Aren't you going to wash your hands?"
FlashLex: "... No... 'cuz I'm EEEVIL!"
Best line of the show happens in the Mens Room in the Secret Society of Super Villains HQ after FlashLex tries to call the Justice League on Lex's Cell phone and is called out of the stall by Dr. Polaris to go to the big meeting to discuss Lex's plans for a huge heist:
Dr. Polaris: "Wait. Aren't you going to wash your hands?"
FlashLex: "... No... 'cuz I'm EEEVIL!"