Supergirl Bosses Explain How The Flash Crossover Is More Than a Gimmick

The announcement last month that Barry Allen (Grant Gustin) would speedster his way to National City to hang out with Kara Danvers (Melissa Benoist) sent a wave of excitement through the Supergirl and DC TV fan universe.

The prospect initially seemed unlikely considering Supergirl and The Flash air on different networks, but producers Greg Berlanti and Andrew Kreisberg were able to pull off the logistical coup in Supergirl's freshman season and Barry arrives in the nick of time on Monday night.

Not only did the producers have to get both networks to greenlight the idea, but they logistically had to find a way for Gustin to film the episode in LA while still headlining The Flash, which films in Vancouver.

Barry shows up organically in Kara's universe at a time that makes perfect sense with her current storyline.

The episode of The Flash that properly explains how Barry Allen made it to National City will air on the CW on Tuesday, one night after the crossover event on CBS.