The show announced before Season 5 that both Jessica Szohr and Taylor Momsen would not return as regular characters and would be downgraded to recurring character status. However, Szohr actually did make future appearances, as her departure was simply related to GG running out of things for her to do. On the other hand, Momsen's unprofessional attitude and toxic relationship with the show's producers made her departure much less amicable: the show referred directly to her issues when announcing her demotion, then let the information that she wouldn't return at all become public (along with sharp criticism of Momsen's behavior by individuals like GG guest star Tim Gunn), and only allowed her to return for the series finale in a scene where Jenny Humphrey is seen in a crowd but has zero dialogue.
Every Gossip Girl episode title is a word play on the title of a movie. This episode refers to Less Than Zero (1987).
David O. Russell (who appears as himself in this episode) has worked as a writer/director/producer on thee movies that starred Jennifer Lawrence: Silver Linings Playbook (2012), American Hustle (2013) and Joy (2015). Jennifer had auditioned to play Serena before Blake Lively had been cast.
It's been shown and mentioned many times that Blair is a fan of Classic American movies. Ethan Peck (David O. Russell's Assistant) is the grandson of actor Gregory Peck, who appeared in one of Blair's favorite movies, Roman Holiday (1953), playing Joe Bradley.