Finally, it's the moment you've been waiting for: The Flash and Supergirl are colliding. But the big crossover you've dying to see may not be what you think. In the appropriately titled "World's Finest," The Flash (Grant Gustin) suddenly appears in Supergirl's (Melissa Benoist) universe, yes Supergirl and Flash are set in alternative universes. Is CBS's Supergirl Earth-3?
Anyway, The Flash appears and helps Supergirl battle Siobhan/Silver Banshee (Italia Ricci) and Livewire (Brit Morgan) in exchange for her help in getting him home to his CW-set show universe. The story comes from Greg Berlanti with a teleplay by Andrew Kreisberg and Michael Grassi. To go along with the network crossover, CBS has created some ultra cute comic book inspired art. It's of course an homage to a classic Superman cover featuring him racing The Flash with other heroes looking on.