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