Special Guest Stars Victor Garber as Dr. Martin Stein / Firestorm Stephen Amell as Oliver Queen / Arrow Emily Bett Rickards as Felicity Smoak Melissa Benoist as Supergirl / Kara Zor-El / Kara Danvers Chyler Leigh as Alex Danvers Caity Lotz as Sara Lance / White Canary Franz Drameh as Jefferson "Jax" Jackson / Firestorm Wentworth Miller as Leonard "Leo" Snart / Citizen Cold Emily Bett Rickards as Felicity Smoak (Earth-X) Melissa Benoist as Kara Zor-El (Earth-X) / Overgirl Stephen Amell as Oliver Queen (Earth-X) / Dark Arrow Jeremy Jordan as Freedom Fighter General Schott Paul Blackthorne as Sturmbannfuehrer Quentin Lance Juliana Harkavy as Dinah Lance / Black Canary Guest Stars Russell Tovey as Raymond Terrill / The Ray Co Starring Brett Alexander Davidson as Nazi Facility Guard Micah Steinke as Nazi Soldier #1 Brian Cook as Nazi Frederick Schmidt voices Metallo-X