In its first season, Supergirl featured only fleeting glimpses of her cousin, the Man Of Steel. While the producers stated that this was to make sure that the focus stayed squarely on Melissa Benoist's Kara, beyond that Warner Bros./DC didn't want Superman to be appearing on the big screen and the small at the same time. Obviously something has changed.
Casting is underway for an actor to play Superman in the first two episodes of the show's second season, with the assumption being that he will show up again occasionally (perhaps on the four-way crossover of Supergirl, Arrow, The Flash and DC's Legends Of Tomorrow?).
Enthuses executive producer Andrew Kreisberg, "Greg Berlanti, Ali Adler and I are beyond thrilled to welcome Clark Kent and his slightly-more-famous alter ego to the world of Supergirl. We cannot wait to see who next dons the red cape!”
Those who have done so previously include Kirk Alyn, George Reeves, Christopher Reeve, Gerard Christopher, Dean Cain, Tom Welling (well, only once..sort of), Brandon Routh and Henry Cavill.