Meg Donnelly will voice Supergirl/Kara, and Harry Shum Jr. will be Brainaic 5. Darren Criss as Superman and Matt Bomer as The Flash are also featured in the cast. The story will follow Supergirl and the Legion of Super-Heroes into the third millennium. Jensen Ackles will be voicing Batman in the upcoming DC’s Legion of Super-Heroes, per The Hollywood Reporter.