Everything you need to know about the Flash-Supergirl crossover

“This is crazy. What are we doing? What are we wearing? Where are we? This is so cool.”

That was the reaction Melissa Benoist recalls upon filming the first take of the long-awaited crossover episode between The CW’s runaway hit The Flash and CBS’ promising newcomer Supergirl. As the Girl of Steel, Benoist has had 17 episodes of flying on wires and battling alien baddies under her cape. But it’s still quite a sight standing opposite former Glee castmate Grant Gustin in Flash’s maroon leather suit 
on location in downtown Los Angeles, where the superfriends prepare to battle a duo of silver-­haired villains hell-bent on Supergirl’s destruction. So just how did the Scarlet Speedster and the Maiden of Might cross paths? In short, superspeed. But let’s go back to the beginning …