Following news that "The Flash" and "Supergirl" will crossover in a March episode of the latter series, many fans were left wondering how the two shows would crossover. Not only do the shows air on different networks, but it's been assumed that the CW's "Flash" doesn't take place on the same Earth as CBS' "Supergirl" since the former show has never mentioned Superman or Supergirl. Now, an Instagram post from "Flash" star (and upcoming "Supergirl" guest star) Grant Gustin drops a hint about how the crossover will come to be.
The episode is titled "Worlds Finest," which is a play on the classic DC Comics series "World's Finest." But instead, the title drops the apostrophe, implying that the crossover will involve multiple worlds. "Flash's" second season has dealt primarily with the discovery of parallel Earths, with the season's villain Zoom as well as a few allies coming from Earth-2. It's possible that the crossover will be facilitated by the Flash journeying to Supergirl's Earth, similar to how he will be traveling to Earth-2 in next week's "Flash" episode.
"Supergirl's" "Worlds Finest" episode will air on CBS at 8 PM ET on March 28.