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 is the first Arrow episode to air on Monday. See more
Kara finds out that Oliver has kryptonite arrows in his inventory. The logistics of this are hard to explain as the substance does not exist on Earth 1, and Team Flash is in possession of the only means of travel to Kara's universe. This means Oliver would need their help in obtaining kryptonite. Moreover, all the kryptonite on Kara's Earth was given to Superman to secure, making it even more unlikely that Oliver would have been able to acquire it. Lastly, Kara is personally offended when she finds out Lena Luthor has kryptonite, but she is far less upset with Oliver for possessing it. 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