DC has a long history in television and film, and CBS is pulling from that to bolster their Supergirl television series.
Deadline reports that Dean Cain and Helen Slater have been cast in "mystery roles" for the upcoming Supergirl television series (could it be as simple as Supergirl's adoptive parents the Danvers?) If you're reading this it's probably a no-brainer, but Cain famously played Superman/Clark Kent in the 1990s television series The Adventures of Lois & Clark while Slater played Supergirl/Kara Zor-El in arguably the first female superhero movie, 1984's Supergirl.
This isn't the first time Warner Bros. have looked to the past for television series. The long-running Smallville's Martha Kent was played by Annette O'Toole, who played Lana Lang in Superman III and of course Christopher Reeve himself appeared on the series. And in the current The Flash series, the previous TV Flash John Wesley Shipp plays father to Barry Allen and Amanda Pays has reprised her role from the 90's series on the new one.
The new Supergirl series is being produced by Warner Bros. TV and Berlanti Productions, who are behind most all of the current DC television series including Arrow and The Flash. Glee's Melissa Benoist is set for the title role, leading a cast which already includes Calista Flockhart, Mehcad Brooks, Laura Benanti, David Harewood and Chyler Leigh. If CBS approves the pilot, its expected to debut as a series as soon as the fall of 2015.