Special Guest Stars Stephen Amell voices Oliver Queen / Green Arrow Grant Gustin as Barry Allen / The Flash Danielle Panabaker as Caitlin Snow Melissa Benoist as Supergirl / Kara Zor-El / Kara Danvers David Ramsey as John Diggle Chyler Leigh as Alex Danvers Rick Gonzalez as Rene Ramirez / Wild Dog Juliana Harkavy as Dinah Drake / Black Canary Tom Cavanagh as Dr. Harrison Nash Wells Elizabeth Tulloch as Lois Lane Ruby Rose as Kate Kane / Batwoman David Harewood as J'onn J'onzz Nicole Amber Maines as Nia Nal / Dreamer Cress Williams as Jefferson Pierce / Black Lightning Jon Cryer as Lex Luthor Tyler Hoechlin as Clark Kent / Superman Marv Wolfman as Autograph Seeker Marv Guest Stars Audrey Marie Anderson as Lyla Michaels Osric Chau as Ryan Choi Reina Hardesty as Joss Mardon / Weather Witch Eileen Pedde as The President Co Starring Raul Herrera as Sargon Tiahra Allen as Baby Sara Diggle Jorden Birch as Worker Marcello Guedes as JJ Diggle Pam Kearns as Female Fan Credit Only Matt Ryan as John Constantine