The Supergirl supporting cast is full of actors who worked on a different DC movie or TV series before appearing on the show. That includes Erica Durance, who played Lois Lane for multiple seasons of Smallville before portraying Kara Zor-El's mother, Alura, on The CW series. However, Alura was originally brought to life by Laura Benanti in Seasons 1 and 2, prior to the role being recast with Durance in Season 3.
A respected judicator (the equivalent of Earth's judges) on Krypton, Alura sent a young Kara to Earth to escape their dying world and watch over her cousin Kal-El, who was younger than Kara at the time. When Kara grew up, Alura continued to provide non-classified information about Krypton to her through an A.I. hologram programmed into Kara's escape pod. In addition to her role as Alura, Benanti also played the character's twin sister and the show's first-season villain, General Astra. After Astra was killed in the Season 1 finale, Benanti made her final credited appearance on the show in the Season 2 episode "Survivors."
Benanti officially stepped away from Supergirl in July 2017, about five months after giving birth to her daughter Ella Rose. Since she lived in New York City and had other work commitments on top of her parental responsibilities, Benanti informed Supergirl's producers she would no longer be able to film her role as Alura in Vancouver, where the show has been produced since Season 2. Benanti commented on her departure on Twitter, saying she loved working on the series and would miss it, but "Right now it's time for me to be supermom to my own little one in NYC."
Following Benanti's departure, Supergirl Season 3 revealed Alura -- now played by Durance -- had survived Krypton's destruction and was living on a remnant of the planet dubbed Argo City. After Kara seemingly defeated the Worldkiller Reign on Earth, she returned to Argo City to live with her mother. However, when Reign re-emerged and Kara finally defeated her for good, she elected to stay in National City and continue to carry out her duties as Supergirl. Alura and Argo City were later destroyed by the Anti-Monitor during the Arrowverse crossover event,"Crisis on Infinite Earths" in Season 5, but were later restored after the Paragons recreated the multiverse.
Since leaving Supergirl, Benanti has remained active in film, television and theater. She replaced Lauren Ambrose as Eliza Dolittle in a Broadway revival of My Fairy Lady from 2018 to 2019, and voiced Lady Cain in Disney's animated Tangled: The Series. She has also had recurring roles on the TV shows The Detour and You and reprised her impersonation of Melania Trump multiple times on The Late Show with Stephen Colbert.
As for Durance, it's unclear what the future holds for her on Supergirl. The show will air its sixth and final season on The CW in 2021, but there haven't been any reports yet about whether Durance will return as Alura or if the character will have a part to play in its remaining episodes. Still, Alura has either shown up, been mentioned or appeared via archival footage in all five seasons of Supergirl to date, so odds are good the show will find a way to give the character a proper sendoff before the series finale.
Returning to The CW in mid-2021 for its final season, Supergirl stars Melissa Benoist as Kara Danvers, David Harewood as Martian Manhunter, Chyler Leigh as Alex Danvers, Nicole Maines as Dreamer, Jesse Rath as Brainiac-5 and more.