Kara Zor-El and Barry Allen met near the end of Supergirl season 1, in a cross-network crossover episode of Supergirl titled 'World's Finest.' There was plenty of comedy, but the episode felt less like a buddy-cop procedural and more like Kara finding an unexpected peer mentor in Barry, who was happy to find a new ally and friend in Kara. For once, he was the superhuman with more experience at taking down bad guys, thus getting to play the elder statesman role.
'World's Finest,' which saw Barry run fast enough to travel to another Earth in the Multiverse, also provided a 31 percent bump in Supergirl ratings up to 7.2 million viewers. Arguably two of the lighter characters in the DC TV universe, their quirky personalities meshed well together. So much so, in fact, Barry's presence was enough to make Jimmy Olsen (Kara's actual crush) jealous.
It wouldn't be the first crossover romance for Barry Allen, considering he had a very brief connection with Arrow's Felicity Smoak in the early stages of The Flash season 1. Despite Grant Gustin's tease at CW Upfronts about Barry and Kara making a "great couple," Melissa Benoist has a different thought. In a DC All Access clip posted on Newsarama, Benoist said:
"I don't know that they'd ever get together. I think they're too similar. I think they'd like pig out on... I think they're pals like, pigging out on ice cream."
In all likelihood, Gustin probably meant that fans could be seeing a lot more Barry and Kara occupying the same space given Supergirl's move from CBS to The CW. While CBS was mum for longer than usual on whether or not Supergirl would get a second season, the move to The CW comes as no surprise given the show is part of the shared Arrowverse. It also doesn't hurt that CBS is one of the parent companies, along with Warner Bros., of The CW.
Not only is the show itself moving, but production will also pick up and head north of the border to Vancouver, BC Canada, where just about every other CW show is filmed (The Vampire Diaries, The Originals, and Reign being the exceptions). With National City, Central City, and Star City all occupying the same space, it seems like Arrowverse masterminds, Greg Berlanti and Andrew Kreisberg, are primed to make The CW their playground.
Supergirl will return for season 2, with The CW as her new home. The show is expected to keep its Monday night time slot.