“Superhero series are always plenty entertaining on their own, but there’s nothing like a crossover episode to spice things up. The three DC shows on The CW have been crossing over regularly, but the upcoming Flash and Supergirl crossover will see The CW and CBS teaming heroes up for the first time. Of course, considering that Arrowon The CW really kicked off the current age of DC on TV, some fans might have expected Oliver Queen to get first dibs on an adventure with Kara Danvers. According to Supergirl executive producer Greg Berlanti, there’s a very simple reason why Barry is the one heading to CBS.
We needed to create a way to do it. We had to introduce Superman since you’ve heard about him and you’ve heard about Supergirl, but in the worlds of Arrow and Flash, they didn’t exist in that world. We introduced the multiverse in The Flash this year, and that was always our way in.
Greg Berlanti’s explanation for the Flash/Supergirl crossover – Superflash, perhaps? – at the recent Paleyfest panel (via Deadline) definitely validates the decision to pick Barry instead of Oliver as the bridge between networks. After all, there are plenty of things that Oliver can do as the Green Arrow that Barry cannot do as the Flash, but hopping between universes is not one of them.
The reveal that Greg Berlanti was looking ahead to a possible crossover with The Flash’s new multiverse certainly makes the prospect more exciting. The crossover was rumored for a long time before it was confirmed, so knowing there was a plan in place for the heroes teaming up means that the episode could be much more than just a stunt…”