The "Wookie gambit" Dreamer mentions is an allusion to the scene in Star Wars: Episode IV - A New Hope (1977) when Luke and Han, disguised as stormtroopers, pretend to have captured Chewbacca in order to access the detention area in the Death Star where Princess Leia is being held prisoner.
First appearances of Izabela Vidovic and Olivia Nikkanen as the younger versions of Kara and Alex since season three's flashback episode Midvale (2017).
Brainy mentions having been shamed for his unawareness of Star Wars: Episode IV - A New Hope (1977) once before. He's referring to a scene in "Battles Lost and Won (2018)" when Kara, quoting Han Solo, expresses her surprise that they've never shown him any of the films in the saga before.
While being tortured, Brainy tries his "little boxes" exercise of compartmentalization, and mentions a Greek story about a box being opened, referring to the mythology of Pandora's box.