While filming on location at a local school for this episode, Chyler Leigh (Alex Danvers) was approached by two little girls who asked her for her autograph. While she was signing the paper that they ripped out of their book, one of them asked her if she's Batgirl. Leigh said she almost claimed the title, but their eyes were so innocent that she told them she plays Supergirl's sister, and they were slightly disappointed. (Source: Clexa con interview 2018 - YouTube)
"Shelter from the Storm" is the song title and a line from Bob Dylan album Blood on The Tracks. The whole line said twice in the song is "she is shelter from the storm" which coincides with the plot and premise of this Supergirl episode.
In Lex Luthor's mansion there is a version of the painting St. Michael Vanquishing Satan.
J'onn's father mistakes Kara for a woman named Ursula and says he does not agree with Kemler regarding the Eradicator Project. In the comics, Eradicator was an alien device designed to preserve its people's history, but the Kryptonian militant Kem-L corrupted it so it was devoted to preserving Kryptonian culture and destroying all others. It was also responsible for altering the DNA of a group of Kryptonian colonists, thus creating the Daxamites. "Ursula" could be a corruption of Ursa from SUPERMAN II, though what connection all of this has with the Martians, if any, is unclear.