Erica Durance played Superman's love interest, Lois Lane in Smallville (2001) and replaces Laura Benanti in the role of Supergirl's Kryptonian biological mother, Alura Zor-El.
This is not Adrian Pasdar's (Morgan Edge) first stint in a super hero series. He played Nathan Petrelli in Heroes, Glen Talbot in Agents Of Shield, and has been the voice of Tony Stark/Iron Man in several animated and video game projects.
In real life, Erica Durance, who plays Kara's mother Alura, is only 10 years older than Melissa Benoist, who plays Kara/Supergirl. However, Alura only appears in dreams, flashbacks and holograms since Kara hasn't seen her mom since she was only 13 years old, and Alura was presumed dead after the destruction of planet Krypton. Therefore it makes sense for Alura to remain unaged in Kara's memories of her. Also, in season 2 it was mentioned by Kal-El (Superman) that Kryptonians age a lot slower than humans.
The musical theme during the rolling end credits is different from that of the first two seasons. This could possibly be related to the fact that the series has added a new member to the music team. For the first two seasons, the "Music by" credit goes only to Blake Neely; added to that name as co-credit in season three is Daniel James Chan. Though Chan had been with the series since its pilot episode, this marked a notable promotion from his previous, uncredited roles in the music department.
This first episode of the third season does not include the Supergirl monologue which introduced episodes in seasons one and two.