Special Guest Stars John Barrowman as Malcolm Merlyn Grant Gustin as Barry Allen Carlos Valdés as Cisco Ramon Melissa Benoist as Supergirl Danielle Panabaker as Caitlin Snow Tom Cavanagh as Eobard Thawne / Harrison Wells / Reverse-Flash Tyler Hoechlin as Dr. John Deegan / Superman (Elseworlds) Guest Stars LaMonica Garrett as The Monitor Liam Hall as Joseph Wilson John Wesley Shipp as Barry Allen / The Flash (Earth-90) Ruby Rose as Kate Kane / Batwoman Jeremy Davies as Dr. John Deegan Cassandra Jean Amell as Nora Fries Bob Frazer as Roger Hayden / Psycho Pirate Co Starring Violet Cameron as GCPD Officer #2 Mick Major as Orderly London A. Morrison as Nurse
