Crossovers are becoming a firm fixture in DC's small screen universe. Arrow and The Flash regularly hop over to one another's respective shows, enriching the fabric of their shared world, and even Constantine paid Oliver Queen a visit despite the demise of his own standalone series. With that in mind, brace yourself for an intriguing new rumor concerning the newest DC kid on the block.

Bleeding Cool reports that a cross-network crossover between The CW's The Flash and CBS' Supergirl is on the cards. The site's sources affirm that CBS intends to commission the "back 9" for Supergirl -- which basically means the show is likely to get an extended first season. If the series does get a bump in episode count, a crossover would apparently be a requirement. Should this unfold as the site describes, The Flash would appear before May's sweeps week. And, it would allow time for Kara's storyline to fully develop. The network previously announced that if any crossovers were to occur, they would arrive well in the future once Supergirl had established itself.

The arc will be inspired by a popular storyline in the comics, in which 100,000 Kryptonians descend upon Earth after being freed from the Bottle City of Kandor by Brainiac. Bringing that to life would eat a big chunk out of Supergirl's budget, so either it'd be a co-funded venture or it's simply not viable for the show. Whichever story they choose, the idea of seeing Supergirl and The Flash join forces is nevertheless an exciting prospect.