Felicity Smoak and Kara Danvers finally address in this episode that they are lookalikes. Ray Palmer comments that Kara looks like a cousin of his, of course, referencing Brandon Routh's role as Superman in Superman Returns (2006).
Sara remarks that "this all started with the two of us", referencing the fact that her affair with Oliver aboard his father's yacht was the incident that began the entire Arrowverse franchise.
Felicity's utterance of the phrase "Darmok and Jalad at Tanagra" from Darmok (1991) is not necessarily gibberish. At the time, she was reacting to being left behind on the ship while the Legends took on the mission, and the phrase she spoke means "working together" in the metaphor-based language depicted in Darmok (1991). Past references from Felicity and Cisco have established the "Star Trek" franchise as existing in their reality, so it's possible that Felicity's disorientated brain was trying to come up with a way to say that she and Cisco should be included in the mission.
Kara Danvers becomes responsible for the creation of the Department of Extra Normal Operations in the world of Arrow (2012) and The Flash (2014). The DEO first appeared in 1998's Batman #550, created by Dan Curtis Johnson and J. H. Williams III. The organization monitors people with extranormal superpowers and to prevent any threat to the general public.
Dig remarks that "things got weird" after Barry showed up in his life, referencing how the tone of "Arrow" shifted from being fairly grounded in realism to a more science fiction/superhero bent after the Flash was introduced.