Greg Berlanti and Andrew Kreisberg, who cast '90s Flash John Wesley Shipp as Barry Allen's father on The Flash, will add former Superman Dean Cain and former Supergirl Helen Slater to the cast of Supergirl, TVLine reports.
Cain portrayed Clark Kent/Superman on Lois & Clark: The New Adventures of Superman, while Slater played Kara Zor-El/Supergirl in the 1984 film adaptation of Supergirl, set in the world of Christopher Reeve's Superman movies. The pair appeared in Smallville as well -- Slater in the role of Lara, Superman's birth mother, and Cain as the immortal Dr. Curtis Knox.
The report says that Slater and Cain have been cast in mystery roles. Laura Benanti of Nashville will play Kara's birth mother, Alura Zor-El, so it won't be a John Wesley Shipp situation...but that doesn't preclude this pair as Superman's parents Jor-El and Lara.
Grey's Anatomy's Chyler Leigh will play Kara's foster sister Alex, Homeland's David Harewood is Department of Extra-Normal Operations director Hank Henshaw, Desperate Housewives' Mehcad Brooks is Jimmy Olsen and Ally McBeal's Calista Flockhart will play Cat Grant, whom TVLine identifies as Kara's boss.