Special Guest Stars Katherine McNamara as Mia Smoak Stephen Amell as Oliver Queen / Green Arrow Tom Welling as Clark Kent of Earth-167 Melissa Benoist as Kara Danvers / Supergirl Elizabeth Tulloch as Lois Lane Elizabeth Tulloch as Lois Lane (Earth-75) Matt Ryan as John Constantine Brandon Routh as Ray Palmer / The Atom Brandon Routh as Clark Kent / Superman of Earth-96 Jon Cryer as Lex Luthor Caity Lotz as Sara Lance / White Canary Grant Gustin as Barry Allen / The Flash Candice Patton as Iris West-Allen Tyler Hoechlin as Clark Kent / Superman Dominic Purcell as Mick Rory / Heat Wave of Earth-74 Guest Stars Wentworth Miller voices Leonard A.I. Kevin Conroy as Bruce Wayne / Batman of Earth-99 Erica Durance as Lois Lane of Earth-167 Audrey Marie Anderson as Lyla Michaels / Harbinger Johnathon Schaech as Jonah Hex of Earth-18 Co Starring Elias Hogewoning as Baby Jonathan Kent Benjamin Hogewoning as Baby Jonathan Kent