Grant Gustin makes his “Supergirl” debut in the first trailer for the upcoming “The Flash”/”Supergirl” crossover episode, “World’s Finest.”

flashcrossoverIn this promo for next week’s episode of “Supergirl,” titled “World’s Finest,” Barry Allen finds his way to National City. While “The Flash”/”Supergirl” crossover was announced recently, this is the first promo to show these two heroes working side by side. 

http://youtu.be/oTtk0pJ07cc