First indirect mention of the not yet existing "Prime Directive". This episode foreshadows more directly the concept, expanding upon brief mentions from Civilization (2001) and other episodes.
Chronologically first mention of the Ferengi, when the Valakian astronaut names warp-capable species they have encountered.
Christopher Rydell, who plays Alien Astronaut, is the son of director Mark Rydell and actor Joanne Linville, who was the first ever female Romulan seen on screen, in The Enterprise Incident (1968).
When Dr. Phlox quizzes Crewman Cutler on human anatomy, Cutler details the workings of the structures of the human heart.
Sadly, actress Kellie Waymire, who portrayed Crewman Elizabeth Cutler in the series, unexpectedly died of cardiac arrest just over a year later, due to a previously undiagnosed cardiac arrhythmia, at age 36.
This episode contains the second mention and first appearance of movie night. The movie being shown is For Whom the Bell Tolls (1943).