You think Zack Snyder and Joss Whedon have it tough with Justice League? Sure, they have to get the DCEU Justice League all working together, but that’s what, six or seven heroes? How about twenty? That’s the task ahead of the teams that create the CW’s superhero shows and the upcoming crossover, “Crisis on Earth-X.”

“I have a limited adventure in the crossover, but I do get to work with a few people that we had a good time,” said DC’s Legends of Tomorrow star Brandon Routh in a recent interview with ComicBook.com. “The best thing that we got to do was the big gathering of everyone here in our world, on the Waverider, which was pretty awesome to have all those superheroes together, and it was a really unique and fun thing I think the audience will like as well.

“We used to get upset about having nine characters on the bridge and figuring out how to shoot that, but having 21 or whatever it is pretty insane,” Routh said. The crossover takes the CW’s heroes to a Nazi-ruled world where they’ll face evil versions of themselves. That takes the heroes from Supergirl, the Flash, DC’s Legends, and Arrow all together, with some bonus appearances.

Confirmed to appear in the episode so far are Green Arrow, Flash, Supergirl, White Canary, The Atom, Citizen Steel, Heat Wave, Vixen, Zari, Firestorm, Vibe, Wild Dog, Black Canary, Captain Cold, and the Earth-X hero The Ray. But we’d expect to see Martian Manhunter, Killer Frost, Kid Flash, Spartan, and Mr. Terrific, as well. Already, we’re getting pretty close to that 20-plus number, and it’s getting ridiculous. The shows’ various supergeniuses like Felicity Smoak will apparently be in the wings, too.

If that sounds like a nightmare to shoot, here’s what Routh had to say about wrangling all these actors:

“Greg Smith, who was our director for our episode, knew what he wanted pretty quick. You have to have your ducks in a row when doing a crossover, because people are coming from four different shows. Like, ‘We have Melissa [Benoist, Supergirl] for 2 hours, and we have Grant [Gustin, the Flash] for an hour, and we have Stephen [Amell, the Green Arrow] for 30 seconds, so you’ve gotta get that shot!”

The “Crisis on Earth-X” crossover event is a two-night feature that begins on November 27 and ends November 28, with Arrow temporarily swapping nights to Monday for the event. Supergirl starts at 8 p.m. EST, followed by Arrow. Tuesday night’s schedule finishes the crossover with Flash and Legends in their usual timeslots of 8 and 9 p.m. EST.