"Dark Frontier" won an Emmy Award for Outstanding Special Visual Effects for a Series. Star Trek nearly swept the category that year; also nominated for it were Thirty Days (1998), Timeless (1998), and What You Leave Behind (1999).
This episode marks the first and only appearance of the Borg probe in a Star Trek series.
Seven is seen in her burgundy-tone bodysuit for the first time here. This outfit was introduced because the previous blue one had been difficult to film against blue screen backdrops.
The Hansen logs indicate that Federation knowledge of the Borg existed prior to the events of Q Who (1989), citing the limited information as "rumor and sensor echoes." No doubt the El-Aurians must have been a source of at least some of the knowledge, since the USS Enterprise-B witnessed their escape after the Borg had destroyed their home in Star Trek: Generations (1994). The knowledge goes back even further: in Regeneration (2003), 212 years before 'Q Who', the crew of the Enterprise NX-01 defeated a time-traveling Borg squadron; however, since these Borg never identified themselves as such, it remains doubtful whether the Hansens were privy to this information.
This episode originally aired as a feature-length episode but it was later broken up into two parts for reruns in syndication.