Ever since CBS' Supergirl series was announced there has been speculation it would eventually lead to a crossover with CW's The Flash and Arrow. Since nothing can ever be allowed to exist in its own universe anymore, especially when superheroes are involved, it was pretty much inevitable. And now fans who have been clamoring to see these these heroes fight evil side-by-side are getting what they asked for. Mostly.
CBS has confirmed that The Flash's Grant Gustin will speed to National City for an episode of Supergirl to be aired on March 28th. Details are being kept under wraps at this point, but one can probably expect Supergirl's Melissa Benoist to eventually return the favor, since Gustin and Arrow star Stephen Amell frequently hop back and forth between one another's shows.
“We are so incredibly excited to announce something that we have dreamed of happening since we starting making Supergirl —The Flash and Supergirl are teaming up!” said The Flash and Supergirl executive producers Greg Berlanti and Andrew Kreisberg. “We want to thank Grant Gustin for making the time to come visit (on top of his already immense workload) and all of the folks at CBS, The CW, Warner Bros., and DC for working this out. And finally thanks to the fans and journalists who have kept asking for this to happen. It is our pleasure and hope to create an episode worthy of everyone’s enthusiasm and support.”
To my mind this is a good news/bad news scenario. While it's great for fans to finally see their favorite TV universes merged together, the bad news is that Supergirl is still kind of terrible, and Barry Allen will probably be really badly written.