(Photo: Warner Bros. TV/The CW)

This weekend, Justice League will "unite the seven" but in just about two weeks, The CW's DC Universe shows will bring far more superheroes than that together in one place.

...Well, maybe it's much sooner or much later than two weeks, because that place is on board the bridge of the time-traveling spacecraft known as the Waverider.

"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. "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 of those superheroes together, and it was a really unique and fun thing which I think the audience will like as well."

The crossover in question is "Crisis on Earth-X," a storyline that sees the heroes of Supergirl, The Flash, Arrow, and Legends of Tomorrow squaring off against a group of doppelgangers of themselves from a universe where Nazis won World War II.

The size of the gathering is a matter of some debate -- depending on who you asked during our visit to the sets of The CW's DC Universe shows last week, different actors would peg it as anywhere from 21 to 35 heroes standing on that bridge -- but Routh and executive producer Phil Klemmer have both landed on 21 or 22 during recent interviews.

"We used to get upset about have nine characters on the bridge and figuring out how to shoot that, but having 21 or whatever it was is pretty insane," admitted Routh. "But 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 for 2 hours and we have Grant for an hour, and we have Stephen for 30 seconds,' so you've gotta get the shot!"

Superheroes confirmed or assumed to appear in the crossover include Green Arrow, The Flash, Supergirl, White Canary, The Atom, Citizen Steel, Citizen Cold, Heat Wave, Zari, Vixen, Firestorm, The Ray, Vibe, Wild Dog, Black Canary, and "civilian superheroes" like Felicity Smoak and Iris West.

The "Crisis on Earth-X" crossover follows in the footsteps of last year's "Invasion!" three-parter, which brought Supergirl to the world of The Flash, Arrow, and Legends but did not include a full-on fourth episode. It will take place on November 27 and 28, for two hours each night, beginning at 8 p.m. ET/PT on The CW.