“The Day of the Dove” contains a hint of Star Trek’s future in its depiction of Klingon-Federation cooperation against a common foe. In fact, it is
this episode that makes the events of Star Trek VI: The Undiscovered Country seem so out of line.
In “The Day of the Dove,” Kirk is the only one who manages to overcome the emotional influence of the alien energy creature, which causes everyone else to feel
racial bigotry towards the Klingons.
“The Day of the Dove” features the first and only appearance in TOS of either Klingon women or Klingon transporters (which are silent).
Susan Howard, perhaps best known as Donna Culver (Krebbs) on Dallas, portrays Mara, one of two Klingon women to appear in “The Day of the Dove.”
In spite of Koloth’s statement in “The Trouble with Tribbles” that Klingon ships do not carry
“non-essentials” (by which he meant females), Mara is Kang’s wife & science officer. Mara is also the only Klingon woman in TOS with a name & dialogue.
“The Day of the Dove” features Michael Ansara (who also guest starred on Buck Rogers in the 25th Century, I Dream of Jeannie, & Lost in Space)
as the Klingon Captain Kang, a role he reprised in the second-season Star Trek: DS9 episode “Blood Oath” (along with two other TOS-era Klingons).
In spite of Kang’s statement at the outset of “The Day of the Dove” that “we have no Devil, Kirk,” both Fek’lhr & Gre’thor, which
appear to be nothing less than the Klingon versions of Satan & Hell, appear in the fourth-season TNG episode “Devil’s Due.”
“The Day of the Dove” is the first & only episode of TOS to feature the hazardous process of intra-ship beaming.
“The Enterprise Incident” showcases Spock romancing an unnamed Romulan commander & Kirk feigning insanity & death & ultimately
donning the pointed ears. (The commander does whisper her name to Spock, but we never learn it. The Romulan second-in-command, however, has a
name—Sub-commander Tal.)
“The Enterprise Incident” marks just the third appearance of Romulans in TOS & only the second appearance of Romulans in person.
(“The Deadly Years” showed Romulan Birds-of-Prey but no actual Romulans.)
“The Enterprise Incident” also features the fictitious Vulcan death grip & the first appearance of the Klingon D-7 Battlecruiser
(used by the Romulans).
“The Enterprise Incident” has Starfleet behaving in an uncharacteristically aggressive, military manner, boldly invading Romulan
space to secure a strategic objective. In fact, Starfleet’s move in this episode is perhaps too risky even for a military operation...
DC Fontana coined the term “cloaking device” in “The Enterprise Incident.” Oddly, the Enterprise crew act as
though they do not recall the Romulan cloaking device from “Balance of Terror”
& “The Deadly Years.”