Legends of Tomorrow: Time travel rules laid out by EP Phil Klemmer

A thick fog wafts through the bars of a cell in a chilly Siberian gulag. At the precipice of an all-out riot, lights flicker fast, sirens likely blaring as Dominic Purcell and Wentworth Miller are in the midst of busting out of jail, but this isn’t a scene from their upcoming Prison Break revival: It’s actually 1986 and their former Flash villains Mick Rory and Leonard Snart are decked out in guard uniforms in order to free a bruised and bloodied Ray Palmer (Brandon Routh) from the clink. Just an occupational hazard in the life of a time traveler.

Brought together by Time Master Rip Hunter (Arthur Darvill), the trio joins a disparate group of heroes and villains — including Sara Lance (Caity Lotz), Martin Stein (Victor Garber), Jay Jackson (Franz Drameh), Kendra Saunders (Ciara Renée) and Carter Hall (Falk Hentschel) — all in the name of preventing immortal threat Vandal Savage (Casper Crump) from taking over the world. (Get the full rundown on each of those characters here.)

But saving the world by jumping from decade to decade won’t be easy, particularly because time travel is fickle. Likening their rules to Back to the Future, executive producer Phil Klemmer explains, “You travel in time, and if you keep your parents from meeting at the Enchantment Under the Sea dance, all of a sudden, you disappear from the Polaroid picture,” he says. The caveat is that whatever is changed doesn’t take immediate effect. “Time is concrete that starts to set,” Klemmer says. “The longer the consequences of that event play out, and once the events of the future are set like concrete, then it’s impossible to change them.”

The other thing that’s impossible to change? “You can’t return to a time and place where you changed the chronology once,” he says. “You basically get one chance to make a change within the timeline, [and then] live with the consequences of that screw-up … It’s like Ghostbusters crossing the streams — if you try to go back and change something [in which] you were a participant, that has a catastrophic effect.”

Hence why the inclusion of time travel doesn’t guarantee safety on this show. “People die, they die for real,” Klemmer says. “You can’t go back and tell them to duck when they got struck by a bullet, because saving their life winds up blurring the entire universe. And if you do find one way of saving the person, there is a cosmic force that’s pushing things towards how [they] were originally meant to happen.”

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Therefore, viewers could see a new group of Legends should the show find legs. “There will be attrition, whether it’s mortal, people lost to the dark side, people lost to geography or time, and people will lose their lives,” Klemmer says. “It is meant to be more of an anthology than the other two DC shows that Greg [Berlanti] has done.”

Jumping through various time periods — the Cold War, Pleasantville ’50s, the Wild West, and the distant future in which Vandal is at the apex of his power, among them — the group uses their palatial time-traveling ship, the chock-full-of-Easter-eggs Waverider, for both their grand plan and personal gain. “Rip has what looks like a Victorian gentleman’s club as his office space,” Klemmer says. “Our art department just packed it to the gills with various DC hidden props — there’s some pretty esoteric stuff in here.”

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There’s also the inclusion of new and familiar faces from the Berlanti-verse, including Damian Darhk (Neal McDonough), Valentina Vostok (Stephanie Corneliussen), Ra’s al Ghul (Matt Nable), Cisco Ramon (Carlos Valdes), Jonah Hex (Johnathon Schaech), and Connor Hawke. “Part of the conceit of the show and going all throughout time is the fact that we can visit all these different corners of the DC Universe,” EP Marc Guggenheim says. “The show functions on a lot of different levels, but one of the levels it functions on is as a love letter to the DC Universe, and Connor is a great example of that.”

And there’s the fact that the chilly gulag the team has escaped from while EW was on set “is familiar to people who watch Arrow,” Klemmer says. “We’ll meet an incarnation of a certain Soviet character 40 years before the time we met him on Arrow.”

Though Legends won’t often crossover with those other shows given the nature of time travel, viewers can expect to see older and/or younger versions of Barry Allen (Grant Gustin) and Oliver Queen (Stephen Amell). “We can go back and see the pre-history of both Arrow and Flash, and we can also go and see what season 50 of Flash or Arrow would look like,” Klemmer says. “But if we return to Star City or Central City, what we’re looking at is not just the future, but an It’s a Wonderful Life future, because in this future, our guys have been gone for 50 years. They left in 2016 never to return.”

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And while running into your past self may not have cataclysmic consequences like ripping a hole in the space-time continuum, there are far worse things that could happen. “It’s more like if you run into yourself, you either make yourself end up in a lunatic asylum, because they’ve seen something totally inexplicable,” Klemmer says, “Or it’s the Doc Brown thing where, [by knowing] of the existence of time travel, you’ve totally altered the future course of your life. A lot of our characters have had such terrible lives that the temptation is too great, and our characters would absolutely have interactions with their former selves, because who wouldn’t want to try to correct the horrible, hideous things that have gone wrong in our lives?” Or make a quick buck by passing along the Grays Sports Almanac? Count us in!

DC’s Legends of Tomorrow debuts Thursday at 9 p.m. ET on The CW.