Go Behind-The-Scenes of "Crisis on Earth-X" in New Video

The CW has released a behind-the-scenes promo for part one of "Crisis on Earth-X", this year's four-show Arrowverse crossover.

The promo gives a brief look at the scope of the event which brings together the heroes of Supergirl, The Flash, Legends of Tomorrow, and Arrow to celebrate Barry Allen (Grant Gustin) and Iris West's (Candice Patton) wedding. Unfortunately, as executive producer Marc Guggenheim says in the promo, things don't go to plan.

"If a superhero gets married, something catestrophic happens to ruin the wedding," Guggenheim explains.

And that "something catestrophic" just happens to be Nazis from Earth-X, a previously unknown Earth considered so horrific no one ever goes to it or talks about it. The Earth-X invaders are bringing that awfulness to Earth-1 in the crossover and that requires a lot of heroes.

"And it's big in every possible way," executive producer Phil Klemmer said. "We were writing scenes where there 22 superheroes."

The promo also gives a look into the writer's room for the "Crisis on Earth-X" and revealed that while writing the never-been-done-before four show event was a huge undertaking, they also found time to have some fun. The writers can be seen enjoying a soccer video game in what Klemmer described as a "summer camp" like environment.

Of course, it's not summer camp for the heroes, but the casts of The CW's DC Comics superhero shows still had a good time making the crossover themselves and Caity Lotz (Sara Lance) says that fans will love what they've put together.

"It's huge," she says. "Fans are going to be super excited about this one."

"Crisis on Earth-X" is a four-hour event that will air on November 27th and 28th beginning at 8 p.m. and running for two hours each day; Supergirl (8 p.m. Monday), The Flash (8 p.m. Tuesday) and Legends of Tomorrow (9 p.m. Tuesday) will remain in their normal time slots but Arrow will move from Thursday to a 9 p.m. Monday placement for the week.