Season 04, Episode 08 – “Crisis on Earth-X, Part 3”
Part 3 of 4. Barry and Iris’s wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes join forces to take on their most formidable villains yet. Earth’s mightiest heroes–Green Arrow, Supergirl, The Flash and White Canary–lead their teams into battle to save the world.
Links: HOMEPAGE – TV.com