Chyler Leigh revealed in an interview that the scene where Alex says goodbye to Winn was Chyler saying goodbye to Jeremy, and she was actually sobbing.
Chyler Leigh was so emotional while filming Alex and Winn's goodbye scene that she had to walk away during takes because it was "hard to look at him."
The episode was previously titled "Supergirl Returns". This was a reference to Superman Returns (2006) which starred Brandon Routh.
This episode was shot primarily at the Vancouver Art Gallery.
The distant relative to whom Brainy refers is implied to be the original Brainiac, also known as the Collector of Worlds, who, in the comics, shrunk and bottled Krypton's capital city, Kandor, to add to his collection of planets deemed worthy of conquest. And while not directly related to Supergirl (2015), the main story arc in the first season of Krypton (2018) is Brainiac's capture of Kandor and the efforts of Kara's grandfather, Seg-El, to stop him.