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Everything You Need To Know About The Flash-Supergirl Crossover

Here's what happens when The Fastest Man Alive meets the Girl of Steel

Who's faster: The Flash or Supergirl? It's the age-old question buried deep in comic book lore. Sure, Barry Allen is a speedster, but Kara Danvers is a Kryptonian, which means she can fly at super speed. Obviously, we're going to need a good, old-fashioned foot race to sort this all out -- and that's exactly what Barry and Kara plan to do when The Flash cruises into National City on the March 28 episode of Supergirl.

Well, that and save the city from not one, but two emerging threats. NBD. (For what it's worth, Barry is still faster because of the Speed Force, duh.)

Look! There's A New Hero In National City

When villains Live Wire (Brit Morgan) and Silver Banshee (Italia Ricci) team up to kidnap Cat Grant (Calista Flockhart), it's up to Supergirl and The Flash, a.k.a. her new metahuman friend from another dimension, to save the day in National City.

Will the crimson-clad duo save Cat and find a way to get Barry home to Earth-1? Clearly, the answer is yes, but it won't be all work and no play for the Scarlet Speedster and the Girl of Steel. After all, fans have been waiting for this magical union for months, so there's no way The Flash leaves National City without doing something adorable with Supergirl. A little harmless flirting? Maybe. Sharing an adorkable laugh together? Most definitely.

Robert Voets/Warner Bros.

Kara and Barry suit up, and we have instant chills.

Supergirl and The Flash's worlds collide when Barry, who's been training to increase his speed in order to fight supervillain Zoom, uses a tachyon device that causes him to run so fast he literally ends up in an alternate

universe. (One that's sprawling with aliens, no less.) There, he meets a down-on-her-luck Supergirl, who's hit a low point in her career as a hero after the red kryptonite fiasco. Lucky for Kara, The Fastest Man Alive knows a thing or two about this hero business, and his pep talks with the Krytonian will not only help Kara get through her superhero slump, but it will also give Barry the confidence he needs to take down Zoom. That is, if he and Kara can save National City from Live Wire and Silver Banshee first.

Robert Voets/Warner Bros.

The Flash helps Supergirl battle Silver Banshee (right) and Livewire (left) in exchange for her help in finding a way to return him home.

Supergirl & The Flash: Fast Friends, Vol. 1

Visually and tonally, Supergirl feels a lot like its speedy cousin on The CW, which makes these two shows perfect crossover companions. Supergirl is fictional, and fantastical, and sometimes, it’s just plain fluff. (It's a welcomed retreat from the nihilism of Zack Snyder's DC Cinematic Universe.) But it's also bright, colorful, and funny -- with moments of real pathos. As the show's bubbly protagonist, Kara is more than just a symbol of strength for the citizens of National City; she's hope personified.

What makes her a great superhero isn’t her super strength or her heat vision. It's her empathy and compassion -- more importantly, it's her ability to triumph in the face of adversity with blinding optimism just like her new speedster friend Barry. Throughout the CBS super-series's freshman season we've watched Kara grapple with what it means to be a hero.

Kara Zor-El wants to be a hero. She wants to live up to her Kryptonian destiny. And she aspires to be like her cousin Superman, so from the pilot episode on -- in which she literally flew into action to save a Boeing 777 from crashing to the ground -- she's been proactive about this hero business. But learning to be a hero isn't easy; in fact, at times, it can seem downright impossible, even for an alien with super strength.

Michael Yarish/Warner Bros.

When Kara meets Barry a.k.a a supernova of everything good and pure in the world.

Meanwhile, in a sea of angsty DC superheroes, Grant Gustin's Barry stands as a beacon of lovable superhero awkwardness. (His nerd-laugh may not be on the same level as Kara's but he's working on it.) More importantly, he challenges the ideals of traditional masculinity; he's a superhero who isn't afraid to cry and be vulnerable. But even The Fastest Man Alive needs to be reminded of his own capabilities every now and then, and helping Kara see her own potential as a hero is just the confidence boost Barry needs in the fight against Zoom.

"He's able to realize that he has more experience than he gives himself credit for," Gustin told EW. "That makes him come back with new confidence and this happiness because of this new friend that's out there."

In many ways The Flash set a precedent for superheroes on TV. The CW series proved that superheroes don’t have to be surly or brooding to get the job done (yep, we're looking at you, Batfleck), and that super-shows could embrace their whimsy without losing their edge. In fact, you'd be hard-pressed to find two heroes more excited to suit up than Supergirl and The Flash.

"What’s so wonderful about these two characters in particular is that they’re so joyful and happy to be heroes," Melissa Benoist told EW. "There's this mutual understanding, respect, and excitement that they found each other."

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A Lesson In Heroing

The Flash and Supergirl are shows that prove that in times of trouble, everyone has the potential to do extraordinary things, and sometimes, The Hero might fail -- even Supergirl and The Flash can't save everyone -- but that's OK. Failure doesn't make Kara or Barry or anyone else any less of a hero; it makes them stronger. Zoom nearly broke Barry earlier this season, and the Scarlet Speedster didn't lie down in defeat. He got up, dusted off his crimson boots, and got back to work. Saving the day isn't always so black and white. Supergirl and The Flash know that all too well.

Finding out who's the fastest superhero alive, however, is an entirely different story. There can be only one winner, and we can't wait to find out who takes the crown. (Just kidding -- we know it's The Flash. Sorry, Supergirl!)