Barry (guest star Grant Gustin) and Iris's (guest star Candice Patton) wedding brings the gang together, but things go awry when villains from Earth-X attack the ceremony. All of the superheroes band together with help from their super friends like Citizen Cold (guest star Wentworth Miller), The Ray (guest star Russell Tovey), Felicity Smoak (guest star Emily Bett Rickards), Iris West and Alex Danvers (Chyler Leigh) to take on their most formidable villains yet. Earth's mightiest heroes - Green Arrow (guest star Stephen Amell), Supergirl (Melissa Benoist), The Flash (guest star Grant Gustin) and White Canary (guest star Caity Lotz) - lead their teams into battle to save the world.
Did You Know?
This marks the first episode in which David Ramsey
(John Diggle / Spartan) does not appear. As such, Stephen Amell
(Oliver Queen / Green Arrow) is the only actor to appear in every episode. See more
Harrison Wells says that there are "53 Karas" in the multiverse, assuming that every person has a doppelganger in every Earth. This has previously been shown to not be true as Harrison's daughter, Jessie, does not have a doppelganger on Earth-1 and when Barry first arrived at Earth-38 he looked up himself and several other characters from The Flash and Arrow and found that they did not exist on Earth-38. See more
[after Green Arrow shoots Overlord Supergirl with a Kryptonite arrow
Is that a Kryptonite arrow? Why do you have a Kryptonite arrow?
In case an evil you ever showed up.
The usual opening narration and title card are replaced by a special "Crisis on Earth-X" sequence. See more
References Legends of Tomorrow