This page contains information regarding Star Trek: Short Treks, and thus may contain spoilers.
Una, also known informally as Number One, was a female Human Starfleet officer in the 23rd century. Since 2254 at least, she served aboard the USS Enterprise as Christopher Pike's first officer. (TOS: "The Cage"; DIS: "An Obol for Charon"). "Number One" was naval slang used by captains such as Pike, and later, Picard, to address their first officers. (TNG: "Disaster")
At some point during her life, Una enlisted in Starfleet and by 2254 was assigned to the USS Enterprise in the command division. By 2254, Una was promoted to the rank of lieutenant commander and was serving under the command of Captain Christopher Pike. As well as being one of the ship's helmsmen, Una was its first officer. (ST: "Q&A")
She was one of the most experienced members of the crew. According to the Talosian magistrate known as The Keeper, she had exceptional intelligence and rationality, while her seeming lack of emotion was largely a pretense concealing fantasies that involved Captain Pike. (TOS: "The Cage")
With Pike kidnapped by the Talosians, Una led the effort to rescue him, first by unsuccessfully attempting to use a laser cannon to blast open an entry to a Talosian underground lair where Pike was being held, and then by using the transporter in an attempt to infiltrate this lair. Una was subsequently kidnapped, along with Yeoman Colt, for the purpose of providing Pike with a mate with whom he could procreate. In response to this, Una set her laser pistol to overload, telling the Talosian Keeper that it was wrong to keep a colony of Humans as slaves, and that they would rather die. This, combined with an examination of the Enterprise's historical records, convinced the Talosians that Humans' unique hatred of captivity made them nonviable subjects, and they were subsequently allowed to return to the Enterprise. (TOS: "The Cage")
Footage of her experience aboard the Enterprise under Captain Pike during the original visit to Talos IV, from 13 years prior, was transmitted from that planet during Spock's fictional court martial aboard the same ship in 2267. (TOS: "The Menagerie, Part I", "The Menagerie, Part II")
Helping out Spock
In 2257, She remained with the ship while it underwent major repairs that year, but briefly visited Pike aboard the USS Discovery to provide him with information on Spock's recent escape from Starbase 5. The two officers sat and talked briefly as Una sat down to a meal in the mess hall. During their conversation, Una admitted that she went through unofficial channels to obtain the information, noting that the entire situation was extremely odd. Una stated plainly that she was not going to let Spock go without a fight and Pike noted that as usual they both were in agreement. Before they parted she warned Pike to be careful and Pike told her the same. She returned to the Enterprise shortly thereafter. (DIS: "An Obol for Charon")
Battle with Control
- Prior to 2254: Assigned to the USS Enterprise under Captain Christopher Pike as first officer
- 2256–2257: Along with the rest of the Enterprise crew, sits out the Federation-Klingon War
"It's wrong to create a race of Humans to keep as slaves."
"Who would have been Eve?"
"Welcome aboard Discovery, Number One."
"Apparently, Enterprise is the only ship in the fleet that's had any problems."
"You know, he warned me. The damn holographic comm system. Tell Louvier to rip out the entire system. From now on we'll communicate using good, old-fashioned view screens. Truth is I never liked the holograms. They look too much like ghosts. He told you I'd say that."
"No. I told him."
"Cheeseburger. Fries. Habanero sauce."
"You want to order some lighter fluid with that?"
"That goes with the shake."
"Welcome home, Captain."
"Good to be back. Wish it were under better circumstances."
"Don't we all."
"All major systems are back online, and we'll have no more holographic communications...ever."
"Probably for the best."
- - Una, Christopher Pike, and Katrina Cornwell, on Pike's return to the Enterprise (DIS: "Such Sweet Sorrow")
"Actually, our odds might be a little better than that. I took the liberty of retrofitting our shuttle and landing pod complement with enhanced phasers, and I commandeered the new experimental tactical flyers, assuming the shit would hit the fan."
"Well done, Number One."
"In English please. I can't blow a path through what you're saying."
"Captain, plans A and B didn't work. We're now into the 'Hail Mary' part of the operation."
"That's been just about everything today."
"Where to, Number One?"
"You're the captain... captain."
"I hear we discovered a new moon at Edrin II."
"That we did, sir."
"Thank You, Number One. In that case, Let's give her a spin... that sound good to you, Mr. Spock?"
"Yes, captain. Let us see what the future holds."
"Ready for warp, sir."
- - Christopher Pike, Una, and Spock, on the Enterprise's next destination (DIS: "Such Sweet Sorrow, Part 2")
|First officers of the starships Enterprise|
|Enterprise NX-01:||Tucker • T'Pol • Sato|
|USS Enterprise:||Pike • Una • Spock • Decker • Saavik (as a trainee) • Thelin|
|USS Enterprise-D:||Riker • Kurn • Shelby • Data • Worf|
|ISS Enterprise NX-01:||Archer|
|ISS Enterprise NCC-1701:||Spock|
|USS Enterprise:||Spock • Kirk|
In an interview with TrekCore, the co-writer of "Such Sweet Sorrow, Part 2" and Star Trek: Discovery third season co-showrunner Michelle Paradise confirmed that Christopher Pike called Number One "Una" in that episode.  Conceivably, it was merely intended as a Romanic-sounding diminutive for "Number One" as a term of endearment, instead of as a proper name. This is one of the many names used for this character in non-canon material. Subtitles on Netflix spelled it as Noona, while the CBSAA captions say that he merely said "and, uh..." while transitioning to a question directed at Admiral Cornwell.
It was rare that an officer with the rank of lieutenant served as the first officer of a starship. The likely reason for this was that, when Gene Roddenberry first created Star Trek, the first rank structure he employed was based on the system used in the 18th and 19th century British navy, in which a ship's second in command was generally a first lieutenant in the sense of the most senior lieutenant, rather than 20th century naval ranks we have come to associate with Starfleet.
In the original version of the series outline Star Trek is... (as reprinted in The Making of Star Trek, pp. 22-30), Number One was initially described as "a glacierlike, efficient female who serves as ship's Executive Officer." (The Making of Star Trek, p. 24) A more detailed description of the character from exactly the same document stated;
- The Executive Officer
- Never referred to as anything but "Number One", this officer is female. Almost mysteriously female, in fact – slim and dark in a Nile Valley way, age uncertain, one of those women who will always look the same between years twenty and fifty. An extraordinarily efficient officer, "Number One" enjoys playing it expressionless, cool – is probably Robert April's superior in detailed knowledge of the equipment, departments, and personnel aboard the vessel. When Captain April leaves the craft, "Number One" moves up to Acting Captain. (The Making of Star Trek, p. 29)
In the scripts of "The Cage", Number One was described as "Female, slim and dark in a Nile Valley way, age uncertain, one of those women who will always look the same between the ages of twenty and fifty [....] Almost glacier-like in her imperturbability and precision. From time to time we'll wonder just how much female exists under that icy facade." She was also scripted to be slightly more wary of J.M. Colt than she is in the final version of the episode, such as being initially reluctant about allowing her to join a landing party assigned to rescue the captain. 
Number One was dropped from the series as NBC executives did not respond well to her character. Reactions to her in the screen test of "The Cage" were also poor (by the women more negatively than the men, according to Gene Roddenberry). Her highly logical, steel-trap mind was given to the character of Spock in TOS: "Where No Man Has Gone Before" and maintained there onward.
Although Majel Barrett-Roddenberry was credited as Majel Barrett in the unaired "The Cage", she was credited as "M. Leigh Hudec" – Barrett's birth name – in the aired two-part episode "The Menagerie, Part I" and "The Menagerie, Part II", because the production team was endeavoring to hide from NBC the fact that the actress, not to be signed for either the second pilot or the regular show as had been demanded by the network, had actually returned to Star Trek: The Original Series as the recurring Nurse Christine Chapel by Gene Roddenberry's doing. (Inside Star Trek: The Real Story, 1997, pp. 223-224; These Are the Voyages: TOS Season One, 1st ed, pp. 25-27) An unintended ironic twist in Star Trek history was that when Roddenberry surreptitiously brought the natural brunette Barrett back on the Original Series, he had her also disguised as a blonde to mislead the NBC network executives, who adamantly did not want her back on the show, whereas the natural blonde Romijn had to have her hair dyed to have her appear as the brunette Number One in Discovery.
In the Marvel Star Trek: Early Voyages comic book series, this character was named Lieutenant Commander Robbins. Her first name was interrupted by other dialogue, but starts with "Eure-."
The novel Vulcan's Glory, by Star Trek: The Original Series writer D.C. Fontana, suggested this character's moniker was not simply a nickname or title – she was an Illyrian who was called "Number One," as the best intellect among her generation. The novels The Children of Kings and Child of Two Worlds explain that Number One does have a given name, but it's difficult to pronounce for non-Illyrians; the former suggests that she liked to be called by this name rather than her own as it enabled her to maintain a professional relationship with her captain. In the novel Captain to Captain she is referred to as "Una." The name "Una" was also used in the Star Trek: Discovery novel Desperate Hours and was used in DIS: "Such Sweet Sorrow, Part 2".
Star Trek II: Biographies gives her real name as Leigh Hudec.
Peter David's New Frontier series of novels had a character named "Morgan Primus" who was an immortal like Flint (from TOS: "Requiem for Methuselah") and was the mother of Robin Lefler. It is hinted that she and Number One are the same person.