The Star Trek: The Original Series episode, “Errand of Mercy” includes the first appearance of one of Star Trek’s most iconic aliens — the Klingons. Throughout its three seasons, TOS produced some truly memorable episodes of television, many of which continue to affect the Star Trek franchise today. The adventures of Captain James T. Kirk (William Shatner) and the USS Enterprise crew laid the groundwork for every Star Trek story that came after. Many of the franchise’s most recognizable aliens made their debut on TOS, including the infamous Klingons.

Star Trek: The Original Series season 1, episode 26, “Errand of Mercy,” sends Captain Kirk and his crew to the planet Organia, as they try to convince the locals to side with the United Federation of Planets rather than the Klingons. As Kirk and Mr. Spock (Leonard Nimoy) speak with the Organians, Klingon forces arrive, forcing the Enterprise to retreat to a safe distance. Kirk then faces off against the Klingon leader Kor (John Colicos), who proves to be an intelligent military strategist. Although the appearance and culture of the Klingons would change a lot over the years, their depiction in “Errand of Mercy” set up everything that came after.

What Happened In Star Trek: The Original Series’ “Errand of Mercy”

Captain Kirk met the Organians & the Klingons for the first time.

In Star Trek: The Original Series‘ “Errand of Mercy,” the United Federation of Planets is on the brink of war with the Klingon Empire, so Captain Kirk and the USS Enterprise are sent to Organia, a planet that sits on the Federation/Klingon border. The Federation hopes to prevent the Klingons from taking advantage of Organia’s strategic location. Kirk and Spock beam down to the planet, initially believing it won’t be difficult to convince the Organians to work with the Federation. The local council leader, a man named Ayelborne (John Abbott), insists that they want no part in any conflict and refuses to take part in any kind of violence.

Soon, a Klingon fleet appears in orbit around Organia, forcing the Enterprise to retreat and leave Kirk and Spock on the planet. The Organians do not make any attempt to resist the Klingons, who quickly take control of the planet, led by Commander Kor. Attempting to inspire the Organians to fight back, Kirk and Spock sabotage the Klingon’s supplies. When Kor tries to torture Kirk and Spock for information, the Organians put a stop to the conflict, revealing their true nature as powerful, non-corporeal beings.

Klingons Debuted In Star Trek: The Orginal Series’ “Errand of Mercy”

John Colicos’ Kor remains one of Star Trek’s most important Klingons.

John Colicos’ Kor made quite an impression as one of the first Klingons to appear on screen, and his performance helped establish the personality of many Klingons moving forward. As Kirk describes the Klingons, they are presented as a “military dictatorship” whose civilization is constantly at war with some foe or another. When Kor arrives on Organia, he immediately declares its people to be “subjects of the Klingon Empire” and enacts a series of laws punishable by death. The Klingons in “Errand of Mercy” are ruthless villains built on outdated stereotypes, but they gained more nuance and characterization in later appearances.

Kor goes toe-to-toe with Captain Kirk, and while he displays a certain level of honor in his dealings, the Klingons of Star Trek: TOS were not known for their honor. Not only do the Klingons subjugate the Organians and order mass executions, but they also try to torture Kirk and Spock for information. The Klingons are depicted as savage conquerors, with little patience for other cultures. As the Organians predicted, however, the Klingons and the Federation would eventually become allies, and while the Klingons remained fierce warriors, they toned down their ruthlessness a bit.

How Klingons Have Changed Since Star Trek: The Original Series’ “Errand of Mercy”

The appearance and culture of the Klingons have received numerous updates over the years.

In both appearance and culture, the Klingons have changed a great deal since their introduction in “Errand of Mercy.” Star Trek: The Original Series was limited regarding budget and make-up, and it wasn’t until Star Trek: The Motion Picture that the look of the Klingons got an upgrade. With longer hair and the now-iconic forehead ridges, Star Trek: The Motion Picture brought the Klingons closer to their most recognizable look. Star Trek: The Next Generation solidified this look, and dove deeper into Klingon culture and tradition with Lt. Worf (Michael Dorn).

Star Trek: Deep Space Nine continued Worf’s exploration of his Klingon heritage, further establishing the honor and tradition at the heart of Klingon society. Like any species, however, not all Klingons upheld this ideal version of their culture. Star Trek: Discovery introduced Klingons of a very different sort, with a controversial new look. Since their introduction in Star Trek: The Original Series, the Klingons have changed perhaps more than any other Star Trek species, but they remain one of the most recognizable fictional species in popular culture.