Most Star Trek characters are humans, or members of well-known alien races, but sometimes, a new main or recurring character will hail from an alien species that viewers have only seen once before. Humans make up the majority of Star Trek characters, with Starfleet being based on Earth, but you’ll find plenty of Vulcans, Romulans, and Klingons throughout the franchise, too, since each of these species originated on Star Trek: The Original Series. The Star Trek timeline marched on into Star Trek: The Next Generation, which introduced its own share of frequently-seen alien species, like adversarial Ferengi or Cardassians, and allies like Bajorans or Betazoids.
Because one of the core missions of Starfleet is seeking out new civilizations, however, a conceit of Star Trek is introducing a new alien species every time the USS Enterprise visits a strange new world. Usually, these one-episode aliens are never seen again after serving their purpose in an episodic adventure, because there’s more space to explore, other alien species to meet, and more stories to tell. Sometimes, however, something about a new alien species is interesting enough to warrant seeing them again, so members of these single-serving species turn up again as regular or recurring characters in newer Star Trek shows.
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Lt. Commander D. Nhan on Star Trek: Discovery
Barzan, from Star Trek: The Next Generation Season 3, Episode 8 – “The Price”
In Star Trek: The Next Generation season 3, episode 8, “The Price”, the discovery of a supposedly stable wormhole in 2366 puts Barzan II on the map, which makes it all the more interesting that Lt. Commander D. Nhan (Rachael Ancheril) is a Barzan serving in Starfleet on the USS Enterprise and the USS Discovery close to a century earlier. Nhan wears the same assistive breathing device as the Barzans in TNG, whose culture emphasizes personal obligation and duty to one’s community due to Barzan II’s lack of natural resources. Nhan shares that attitude, and explains that her people have a penchant for security roles because of it.
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Lt. Kayshon on Star Trek: Lower Decks
Tamarian, from Star Trek: The Next Generation Season 5, Episode 2 – “Darmok”
For all that the highly metaphorical Tamarian language has had an impact on Star Trek fandom, the Children of Tama were only in a single Star Trek: The Next Generation episode, season 5’s “Darmok”, before the arrival of Lt. Kayshon (Carl Tart) in Star Trek: Lower Decks. Kayshon has fortunately mastered Federation Standard, making communication as a Starfleet officer far less of a “beast at Tanagra” and more “Picard and Dathon at El-Adrel”. Although Kayshon is just a recurring character aboard the USS Cerritos, a Tamarian on Lower Decks has the ability to explore that linguistic misunderstanding can lead to comedy, just as TNG showed it as tragedy.
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Ensign Peanut Hamper on Star Trek: Lower Decks
Exocomp, from Star Trek: The Next Generation Season 6, Episode 9 – “The Quality of Life”
When introduced in Star Trek: The Next Generation, the Exocomps are non-humanoid robots capable of adaptive learning and tool production to assist engineers, but one Exocomp’s refusal to follow orders that would place it in harm’s way leads Lt. Commander Data (Brent Spiner) to determine that the Exocomps are actually sentient. And since Exocomps are sentient, they can join Starfleet, like the “mathematically perfectly named” Ensign Peanut Hamper (Kether Donohue) in Star Trek: Lower Decks. A sassy and self-absorbed model who joins Starfleet to anger her father, Peanut Hamper’s calculating self-preservation and various acts of rebellion take TNG‘s Exocomp behavior to the extreme.
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Lt. Hemmer on Star Trek: Strange New Worlds
Aenar, from Star Trek: Enterprise Season 4, Episode 14 – “The Aenar”
In Star Trek: Enterprise, the Aenar are an ostensibly mythical offshoot of Andorians known for their telepathic abilities, with a minimal population limited to the coldest parts of Andoria. Most Aenar are blind, including Star Trek: Strange New Worlds‘ Lt. Hemmer (Bruce Horak), introduced as the Starship Enterprise’s Chief Engineer. Like the Enterprise Aenar, Hemmer demonstrates heightened senses that compensate for his lack of sight, as well as telepathy and some precognition. In mentoring Cadet Nyota Uhura (Celia Rose Gooding), Hemmer exemplifies the Aenar philosophies of pacifism and respect for life, and his personal philosophy of challenging others’ views.
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Zero on Star Trek: Prodigy
Medusan, from Star Trek: The Original Series Season 3, Episode 7 – “Is There in Truth No Beauty?”
Star Trek: The Original Series establishes the non-corporeal Medusans as a species that humanoids can’t look at without going mad, so Ambassador Kollos travels by pod and interacts either through a handler, Dr. Miranda Jones (Diana Muldaur), or a mind meld with Mr. Spock (Leonard Nimoy). In Star Trek: Prodigy, Zero (Angus Imrie) comes from a hive-mind of genderless beings, and inhabits an exosuit that allows them to interact directly with the corporeal world. Instead of being a curious plot device, Zero is one of Star Trek: Prodigy‘s main characters, so their story explores the psychological ramifications of the Medusan capability to induce madness, and also being isolated from others while trying to belong.
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Commander Una Chin-Riley on Star Trek: Strange New Worlds
Illyrian, from Star Trek: Enterprise Season 3, Episode 19 – “Damage”
The Illyrians in Star Trek: Enterprise seem very different from Star Trek: Strange New Worlds‘ Commander Una Chin-Riley (Rebecca Romjin), also known as Number One. Illyrians employ genetic modification as a cultural practice that allows Illyrians to inhabit otherwise uninhabitable worlds, so it’s practically expected that Illyrians from different colonies will look different as a result. The Illyrian ship in Enterprise serves as a plot device, so there’s little information about them as species until Strange New Worlds expands on Illyrian culture through Number One, particularly in Strange New Worlds season 1, episode 3 “Ghosts of Illyria”, and SNW season 2, episode 2, “Ad Astra Per Aspera”.
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Lt. Commander Jadzia Dax on Star Trek: Deep Space Nine
Trill, from Star Trek: The Next Generation Season 4, Episode 23 – “The Host”
The symbiotic Trill have become popular Star Trek aliens, and Trill stories contain metaphors for expressing the rich variety of human gender and sexuality, just as intended in their one episode of TNG. In “The Host”, the humanoid host’s personality is suppressed, so Ambassador Odan (Franc Luz) remains the same person regardless of host. When DS9 changes the Trill, Lt. Commander Jadzia Dax (Terry Farrell) sports a spotted look, and joined Trill are now a blend of host and symbiont personalities. As a regular character, Dax’s relationships build on themes of personal and gender identity that were established but never broadly explored with Odan.
Every one of these returning species represents a unique aspect of the human experience for Star Trek to comment on that has become more relevant than ever. From the Tamarians’ meme-like language and Exocomps’ autonomy, to the further reaching consequences of Illyrian genetic modification, discussions of disability surrounding the Barzans and Aenar, and concepts of gender for Trill and Medusans, the defining traits of some single-serving species are just too broad to be fully explored in just one episode. In those cases, it makes perfect sense for Star Trek to revisit those species with new characters.
Star Trek: The Original Series, Star Trek: The Next Generation, Star Trek: Deep Space Nine, Star Trek: Enterprise, Star Trek: Lower Decks, and Star Trek: Strange New Worlds are streaming on Paramount+. Star Trek: Prodigy is streaming on Netflix.
