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 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 David Harewood as J'onn J'onzz Ruby Rose as Kate Kane / Batwoman Jon Cryer as Lex Luthor Tyler Hoechlin as Clark Kent / Superman Nicole Amber Maines as Nia Nal / Dreamer 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 Marcello Guedes as JJ Diggle Raul Herrera as Sargon Tiahra Allen as Baby Sara Diggle Jorden Birch as Worker Pam Kearns as Female Fan Credit Only Matt Ryan as John Constantine