Iris and Barry are getting married! The DCTV crossover this year is bigger than ever when Westallen and their friends from Supergirl, Arrow, The Flash, and Legends of Tomorrow gather for their grand wedding during the four-hour crossover, "Crisis on Earth-X." Unfortunately for Iris and Barry, their wedding won't go smoothly when it's interrupted by a few familar faces from Earth-X.
The official episode description from the CW says, "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."