Brian Truitt

USA TODAY

The superhero crossover has been a staple of comic books for decades, ever since the first young fanboy who wondered if Batman could take down Superman in a fight.

They were a staple of Greg Berlanti's childhood, too, and he brings his small-screen DC Comics do-gooders together for an adventure that starts in The CW's The Flash Tuesday (8 ET/PT) and then continues on the network's Arrow series Wednesday (8 ET/PT).

"One of the things I like to do with the shows is to honor the DNA of comic books, and at least in my experience, comic books are the originators of the crossovers and the mash-ups," says Berlanti, executive producer of both shows.

Barry Allen (Grant Gustin), Central City's fastest man alive, is no stranger to Oliver Queen (Stephen Amell), Starling City's resident vigilante — Barry first appeared on Arrow's second season a year ago, an introduction to the young hero before his own Flash show debuted to record ratings in September.

The shows have traded characters since then — for example, Queen confidante Felicity Smoak (Emily Bett Rickards) recently took a train ride to visit Barry and his pals at STAR Labs, Dr. Wells (Tom Cavanaugh), Caitlin Snow (Danielle Panabaker) and Cisco Ramon (Carlos Valdes).

In the crossover, the Flash's crew reaches out to Oliver and his team — Felicity, Diggle (David Ramsey) and Arsenal (Colton Haynes) — to deal with a superpowered threat in Starling CIty, but everybody also convenes to track down Digger Harkness, a character who wields high-tech boomerangs and is based on one of the Flash's Rogues from the comics.

There's teamwork but also some friction between the heroes. "It's like that age-old thing, like who would win: Batman or Superman?" Amell says. "Well, Superman would fly him up to space. And who would win, Flash or Arrow?"

So how does even a physical specimen of a bowman deal with somebody who could move at Mach 1? Oliver has to use his experience and play on Barry's overconfidence, according to Amell.

Plus, Barry may not take him seriously and the same goes for his team, the Arrow star says. "That's something we touch on in the crossover: Everything's cool in Central City and you're giving your villains funny nicknames but these are life-and-death situations and you have to remember that."

Adds Gustin: "When it comes down to regular old fistfighting, Oliver's probably going to kick Barry's ass."

Even though both shows live in a shared universe, keeping the tones of both — the dark and violent Arrow compared to the brighter Flash — was important in the crossover, according to the Flash actor.

Berlanti sees a certain Robert Redford/Paul Newman quality in their on-screen chemistry, but both of his stars feel that their characters bring out different aspects in each other.

The emerald archer "brings out Barry's stubbornness because Oliver's so stubborn. They butt heads and he brings out the Oliver in Barry," Gustin says.

And Amell feels that the Flash brings out a lighter, humorous side in Oliver, as well as reminding him of the innocence he's lost.

"There's an enthusiasm about Barry that Oliver finds endearing," says Amell, who's discovered a certain rhythm working with Gustin in scenes on both shows and in the crossover.

"Because of the character he plays and because of our places in the DC Universe, it just feels special. It feels a little bit bigger."

That epic scope is what appealed to Berlanti about comics when he started reading them in the mid-1980s, specifically two major crossover events: Marvel Comics' Secret Wars and DC's Crisis on Infinite Earths, a story line hinted at in Flash episodes.

"It was like one string of mash-ups of all the characters circling through each other's worlds," Berlanti says. "The canvas felt so big and unpredictable because you had all these different characters together at the same time."

With everything from NCIS and CSI meet-ups to The Avengers movie, Berlanti sees the crossover as an important part of the current pop-culture zeitgeist — and it's why he's not ruling out a superhero three-for-all if everything goes well with his in-development series Supergirl for CBS.

"Probably more than anything, I like to be a part of making these shows because it does remind me of growing up," Berlanti says. "And I want the audience to be a part of what I experienced."