Powered by comic-book physics (and bags of money), the superhero universe is always expanding. It’s true in movies (hey, didja see that Suicide Squad trailer?), and for the past half-decade it’s been true on television as well, with Marvel spreading all over Netflix and ABC, and DC Comics metastasizing across The CW with Arrow and The Flash. Last night, the "Arrowverse" expanded yet another notch with the premiere of Legends of Tomorrow—and in doing so, furthered what is already one of the most interesting hero universes in pop culture*.*

The show's time-travelling premise means that protagonist Rip Hunter is able to pull from their timelines a who's-who of oh-right-them DC supporting players—Hawkman and Hawkgirl, the Atom, Firestorm, the Black Canary, Captain Cold, and Heatwave—to chase immortal Vandal Savage across various eras. As far as comic-book team-ups with a huge period-costume budget, it's a damn sight better than *League of Extraordinary Gentlemen. *In fact, if you like Arrow and Flash, you’ll like Legends of Tomorrow, full stop. It has the same sense of humor, the same dextrous continuity with the other shows and DC at large, and a bunch of actors who are pretty damn charming in silly outfits, shooting well-rendered flames from their hands or crunching badguy bones hand-to-hand.

If you're a Doctor Who fan, you’ll probably also enjoy Arthur Darvill, who played the Doctor’s companion Rory for a couple years, as Rip Hunter. Hanging out with a dashing British man in a long coat who has a vessel that can camouflage itself and travel in both space and time has clearly equipped Darvill to play a dashing British man in a long coat who has a vessel that can camouflage itself and travel in both space and time.

But what’s most interesting about Legends is the expansion of the DC TV story universe—what I called a paracosm in my December story about Star Wars. The three shows share writers and producers, and in fact “Arrow is at one end of the hallway, Legends is in the middle, and Flash is at the other end,” says Andrew Kreisberg, an executive producer on all three shows. “And Supergirl is right upstairs.” (It’s on a different network, CBS, but Kreisberg is an EP on that show, too.) “You’ll say, ‘wait, what episode of Arrow are they doing X in?' and by the time somebody gets on the phones to call down the hall it’s just as easy to get up and ask them.”

Despite their differences in tone---Arrow is a darker show than Flash, and Flash almost always has a scene where a father and son cry about how much they love each other---the writing team has been careful and smart about how the shows integrate. Every season has a crossover two-parter. The characters seem to remember how they know each other. “Part of the fun, and this is really the last step whenever we break a story or write a script, is just to check our math and see if there’s a connection between the various shows we could make because it’s cool, or that we should make,” says Marc Guggenheim, an EP on Arrow and Legends of Tomorrow. “You do it too much and it’s distracting. You do it the right amount, and it’s a nice thing the audience can appreciate.”

One of the things the Arrowverse has done best is integrating versions of B- and C-list characters. Firestar and Black Canary both had a heyday in the mid-’80s, as did early Arrow antagonist Deathstroke. “The reason it’s so organic is that in large part the gatekeeper on these decisions is Geoff Johns, who we’re all friends with,” says Guggenheim. Johns is chief creative officer at DC, and a prolific comics and TV writer himself. “If we have an idea in the writers’ room I can send him a quick email and say, ‘hey, can we use Jonah Hex on Legends?’”

The answer was yes, by the way.

So what happens next? “There’s a lot of time and money put into casting, costume design, thinking about the character and where we could use them,” says Guggenheim. “That’s a lot of financial and creative bandwidth.” The result, though, is that if a character works, having him or her return to the show isn’t as much of a lift—and it made it possible for those characters to disconnect from their home shows and reassemble on Legends.

And because the show time-travels, the continuity knot of the Arrowverse doesn’t really get any more tangled. “Once everyone gets on board the Waverider, the time-traveling spaceship, they’re pretty much taken out of time and thus out of our regular show continuity,” Guggenheim says.

All of which sounds great, in theory. Characters from two well-executed superhero shows get to visit various eras in history, some of which will come from DC Comics’ back catalog of historicals. Jonah Hex’s weird Old West, confirmed. I’m hoping for some World War II action, myself. Sgt. Rock? Blackhawks? Haunted Tank? Come on, let’s do this, right?

But that elides the fact that this DC Comics universe isn’t the only one. That Suicide Squad trailer I mentioned up top? The Arrowverse has a whole other version of the team of badguys called the Suicide Squad. Over on Fox's Gotham, Batman is just a kid who hasn’t caped up yet. And in *Batman vs. Superman, *he’s a middle aged dude fighting Superman. And he used to be Christian Bale.

I’ll make it worse. The head of CBS says Supergirl might cross over into the Arrowverse. Or maybe not. John Constantine, the hero of Hellblazer, cancelled off of yet another network, visited Arrow. And—deep nerd with me now—how come on Arrow the Green Arrow takes his shirt off and has a swordfight with the villainous Ra’s al-Ghul? In the comic books, it was Batman who did that!

Sorry, my glasses slipped down my nose a little bit there. Let me just push them right back up.

So…what’s the real world, here? “What’s been fun for us---and Geoff Johns always says the same thing to be about comic books---is to take on some hero who’s been forgotten and rehabilitate him,” Kreisberg says. “There’s obviously certain things we’re not allowed to touch on, but we don’t dwell on that. We’re thankful for the things we are allowed to touch on. There’s a lot more in the DC universe than Superman, Batman, and Wonder Woman.”

That love for the back catalog actually strengthens the paracosm effect. “What’s so fun about these shows is seeing who pops up. It makes them feel lived in,” says Kreisberg.

Really, comic book fans have known how to handle superhero universe expansion since the very first crossover. Back in the 1980s, as Kreisberg points out, no Batman fan complained when Frank Miller's version of the hero in The Dark Knight Returns didn’t quite jibe with Alan Moore's in The Killing Joke (or the one in the ongoing monthly series). They were all good. They were all Batman. Paracosms, perhaps, only grow and thrive when they outgrow their original creators. Rip Hunter, the comics character, was introduced in 1959. But now, finally, he really does belong to the ages.