Brainiac (recurring guest star voice Corey Burton), once Krypton's all-knowing planetary computer, comes to Earth as part of his information-gathering trek across the galaxy. But, as Superman discovers, Brainiac's intent after gathering the world's knowledge is to destroy the Earth.

Superman masquerades as Batman to confront Roxy Rocket (guest star voice Charity James), Penguin (guest star voice Paul Williams) and a host of other bad guys who are on a crime spree in Gotham City during the real Batman's (guest star voice Kevin Conroy) mysterious absence.

In Clark's hometown of Smallville, a teenage Clark Kent (guest star voice Jason Marsden) teams with Chameleon Boy (guest star voice Jason Priestly), Cosmic Boy (guest star voice Chad Lowe) and Saturn Girl (guest star voice Melissa Joan Hart) from the New Legion to battle Brainiac (recurring guest voice Corey Burton).