Summer Glau was providing the voice for Supergirl in the animated movie Superman/Batman: Apocalypse. A voice role that will forever earn her a place in the hearts of Supergirl fans around the world. The film, based on popular DC Comics stories, begins with the arrival of Supergirl  and she met Superman and Batman (Tim Daly and Kevin Conroy, reprising their roles) which are trying to help her adapt to a new world and her new powers. Wonder Woman also takes her under her wing, but all of their efforts are derailed when Darkseid (Andre Braugher) intervenes and manipulates Kara for his own evil purposes. It ends with Superman's official introduction of his cousin Kara Zor-El, "or as the world will come to know her, Supergirl."
 

This was a Summers very first voiceover/animation experience. She loved the experience just working with her voice and could not think of an animated character that she would like to do more. Because Supergirl is amazing.
 

Warner Premiere released a 12-minute behind-the-scenes look at movie: