Special Guest Stars David Ramsey as John Diggle Stephen Amell as Oliver Queen / Arrow Melissa Benoist as Supergirl / Kara Zor-El / Kara Danvers Tyler Hoechlin as Clark Kent / Superman Guest Stars LaMonica Garrett as The Monitor Elizabeth Tulloch as Lois Lane Jeremy Davies as Dr. John Deegan Co Starring Klarc Wilson as Officer Jones Paul Lazenby as Tech Thief #2 Angela Vanderwal as Heckler Uncredited John Wesley Shipp as Barry Allen / The Flash of Earth-90