Special Guest Stars Caity Lotz as Sara Lance Grant Gustin as Barry Allen Melissa Benoist as Supergirl Danielle Panabaker as Caitlin Snow Melissa Benoist as Kara Zor-El (Earth-X) / Overgirl Tom Cavanagh as Harrison Wells Tom Cavanagh as Eobard Thawne / Reverse-Flash Chyler Leigh as Alex Danvers Victor Garber as Martin Stein / Firestorm Candice Patton as Iris West Franz Drameh as Jefferson "Jax" Jackson / Firestorm Dominic Purcell as Mick Rory / Heat Wave Colin Donnell as Tommy Merlyn (Earth-X) / Prometheus Uncredited Stephen Amell as Oliver Queen (Earth-X) / Dark Arrow
