Just as Stephen Amell (for the title role of Arrow (2012)) and Grant Gustin (for The Flash (2014)), Melissa Benoist was the very first of a thousand actors to audition for the role of Supergirl.
The Supergirl costume was designed by Colleen Atwood, who also designed the costumes for Arrow (2012) and The Flash (2014). She had previously designed the Superman outfits that would be used in the failed film "Superman Lives" which would star Nicolas Cage in the title role.
Tyler Hoechlin (Clark Kent/Superman) went to prom with Katie Cassidy who portrays DC Comics character Dinah "Laurel" Lance/Black Canary/Black Siren in Arrow (2012) and The Flash (2014).
Reunites Helen Slater, who played the title character in Supergirl (1984), and Dean Cain, who portrayed Superman in Lois y Clark: Las nuevas aventuras de Superman (1993). Both also have previously appeared in Smallville (2001), where Laura Vandervoort portrayed Kara Zor-El/Supergirl. Additionally, Teri Hatcher, who portrayed Mon-El's mother Queen Rhea, played Lois Lane in Lois y Clark: Las nuevas aventuras de Superman (1993) and later Ella Lane in Smallville (2001). Lastly, Kevin Sorbo, who portrayed Mon-El's father Lar Gand, was set to star with Teri Hatcher in Lois y Clark: Las nuevas aventuras de Superman (1993), but ended up losing the role to Dean Cain.
In Myriad (2016), Cat Grant says to tell "Harrison Ford she is flattered but she does not date older men, especially when they're married." Calista Flockhart, who plays Cat Grant, is 22 years younger than her husband Harrison Ford.