The Star Trek Expanded Universe is an official, created term to describe an extrapolation of events which occur in the Star Trek Universe outside the scope of the television series, feature films and novels. Information from the Star Trek "Expanded Universe" typically fills "holes" and is considered to be “canon” in the Star Trek story and timeline, with explanations of events which have never been adequately explained through live action productions. The term was first used in 1966 by writer D.C. Fontana to describe information put forth in the backstory of Doctor Leonard McCoy.
Although original Star Trek fiction (for adult audiences) dates back to James Blish's 1970 novel Spock Must Die!, published by Bantam Books, the publishing company Simon & Schuster is most directly responsible for contributing to the Star Trek Expanded Universe through its license with Pocket Books which has generated many Star Trek novels over the past twenty-five years. Information in the novels, while sometime contradictory, often serves to provide information to the Star Trek Expanded Universe.
The term "Star Trek Expanded Universe" is not an official usage of Paramount Pictures, Simon & Schuster, or any other Star Trek licensee. The term is occasionally used within fandom by analogy with the Star Wars expanded universe as defined by Lucasfilm. However, the policies and practices pertaining to licensed Star Trek fiction are not identical to those used by Lucasfilm. For example, unlike in Star Wars fiction, there is no overall effort among the various licensees to integrate all Star Trek fiction into a single continuity. Although the majority of Star Trek novels in recent years have been written to be consistent with one another and with certain Star Trek comic books, they remain incompatible with many earlier novels and comics, and occasionally with contemporary novels as well.
Many of these premises have been accepted by Star Trek fans as being canon, even though Paramount Pictures, owners of the Star Trek franchise, considers only live-action television and film productions to be canon. This has led to conflict on occasion when a TV episode or film contradicts well-established Expanded Universe backstory (most notably in the case of the prequel series, Star Trek: Enterprise).
- Leonard McCoy's Backstory: Leonard McCoy was married shortly before obtaining his medical degree. Starting a private practice, McCoy fathered a daughter before being divorced by his wife and losing custody of his child. Sometime after 2260, he closed his medical practice and accepted a staff officer's commission in Starfleet to escape the pain of losing his wife and daughter.
- Second Five Year Voyage of the USS Enterprise: Following the events of Star Trek: The Motion Picture the Enterprise embarked on a second five-year mission of exploration. James T. Kirk did not regain his rank of rear admiral but chose to remain a captain to command the Enterprise. The aborted television series Star Trek: Phase II was to have been set during this second five-year mission, and there remains a "gap" between the first and second Trek feature films that suggests such a mission might have occurred, though this has never been confirmed in any canonical resource. Stories that are set in this timeframe do not necessarily conform to any known episode storyline that was planned for Phase II.
- Chekov's Promotion History and Later Life: Ensign Chekov was promoted to lieutenant junior grade at the conclusion of the first five-year voyage of the Enterprise. By 2271, he was a full lieutenant. He obtained the rank of lieutenant commander during the second five-year voyage of the Enterprise and, in 2276, was promoted to commander and assigned as the executive officer of the USS Reliant. He appeared apparently as a retired commander in Star Trek Generations, but later novels and fan sources from Star Trek: The Next Generation indicate that he eventually became an admiral. Walter Koenig also has been quoted as saying at science fiction conventions that he speculates often if Chekov is in some way related to Worf's adoptive Russian parents.
- Physical Appearance of the Romulans: The ruling class Romulans of the 23rd century were referred to unofficially as Romulans of the "Smooth Brow". These Romulans were direct descendants of the original Vulcan dissidents that left Vulcan circa AD 1 (Earth Calendar). By the mid-24th century, the Smooth Brow Romulans had lost most of the power on Romulans to be replaced by standard Romulans who, through centuries of inbreeding and off-world marriages, had developed very pronounced forehead ridges. These Romulans occupied most positions of power in the 24th century government and military; however, the Romulans of the Smooth Brow could still be found in the public light. Commander Sela, a Romulan-Human cross, was often mistaken by fellow Romulans as a Smooth Brow. Ambassador Spock was also able to infiltrate Romulan society by posing as a Smooth Brow Romulan.
- The Riker-Troi Romance Backstory: Although various hints have appeared in sundry Next Generation episodes, only the novel Imzadi actually told the whole story of how Riker and Troi originally met and fell in love - and of what came between them.
- Further Adventures of the Deep Space Nine crew: After the disappearance of Benjamin Sisko and the conclusion of the war with the Dominion, the planet Bajor joins the Federation. Kira Nerys is given permanent command of the station and a Starfleet commission of captain. Many new crew members join DS9, including Elias Vaughn (the station's new executive officer, and commander of the Defiant), Ensign Thirishar ch'Thane (the new Andorian science officer), Lieutenant Sam Bowers (tactical), and others. Sisko eventually returns to corporeal existence and moves with his family to Bajor. (See Deep Space Nine relaunch for further information.)
- James T. Kirk's resurrection: Shortly after Star Trek Generations, William Shatner and co-writers Judith and Garfield Reeves-Stevens wrote a series of novels taking place after the events in the movie, bringing James T. Kirk back from the dead, much like mainstream comic books. While the novels are not mentioned in regular continuity, they are often read by fans who felt Kirk had died an "unheroic" death and deserved something more. Many fans accept these novels into their own fanon continuity (or at least choose to accept The Return only, the most important and commercially successful of the novels). In these, Kirk is venturing in the 24th century, while falling in love again, having a child, getting along with Spock, Leonard McCoy and, also temporally misplaced, Scotty, while also getting himself into new adventures with them, and developing a nice friendship with Jean Luc Picard. They even take a vacation trip together, in The Captain's Peril, shortly after the Dominion War's end, a few months prior to Star Trek: Nemesis. Critics cite an overdone focus on Kirk as the glorified hero, often leaving Picard and others in downplayed roles. These novels, which are not considered part of the overall continuity of the other Star Trek novels, are collectively referred to by fans as the "Shatnerverse."
Star Trek: New Voyages, also uses the idea of Kirk living on in that both released episodes feature possible futures, The pilot "Come What May" features a scene where Kirk sees his possible future. This includes most of the more famous movie scenes (Spock's death, and parts of Star Trek VI: The Undiscovered Country) and then Spock speaking the works "Captain Kirk is alive" just after a repeat of Kirk's last line in Generations. In addition episode one ("In Harm's Way") features Kirk and Spock traveling back in time to help their younger selves; the year they come from is given as 2373, or two years after Kirk's "death" (and roughly the time period Shatner's third novel Avenger gives for Kirk's reappearance on the Galactic stage).
- Charles 'Trip' Tucker's life: In "These Are The Voyages...", the final episode of Star Trek: Enterprise, Charles 'Trip' Tucker is apparently killed defending his ship against alien pirates. The latest Enterprise novel, Last Full Measure, revealed in its final scenes that Trip actually survived the attack and lived on after the events of this episode. It is unknown at present how Trip survived, who ordered that his death be faked, or why. The Enterprise novels are currently undergoing a relaunch similar to that of DS9, so it is possible that these questions may be answered.
- Physical Appearance of the Klingons: The marked difference in the physical characteristics of the Klingons, as seen in Star Trek: The Original Series and in later feature films and television productions, was first explained as the result of a genetic engineering experiment which took place approximately between the year 2210 and 2270. In an attempt to emulate humans, and make infiltration in human regions of space easier, the Klingon Empire merged human DNA with a large segment of its military force. The result was the "Klingon-Human Fusions" who were the only Klingons permitted to have contact with the Federation. By 2271, this attempt at creating Klingon-Human Fusions had been abandoned and the Empire abolished the project. Certain high ranking Klingons (such as Kor, Koloth and Kang) were permitted to undergo procedures to remove the human DNA from their cell structures and revert to a pure Klingon appearance. To this day, the Klingon Empire considers the attempts at creating Klingon-Human Fusions to have been an embarrassment and it is "not discussed" with outsiders. An alternate explanation was offered in the DC Comics graphic novel, Debt of Honor which suggested the ridged Klingons were a different race than the human-like Klingons, which had suffered discommodation at some point. In a two-part episode of Star Trek: Enterprise, aired in 2005 as "Affliction" and "Divergence", this premise was disproved and it was revealed that the change in Klingon appearance was the result of a virus that resulted from military enhancement experiments. Presumably a cure was found for the condition (which was passed from generation to generation) sometime prior to Star Trek: The Motion Picture. Dr. Antaak had one line toward the end of "Divergence" stating that perhaps he could specialize in cosmetic surgery. This would explain how Kor, Koloth and Kang changed their appearance from smooth brow in The Original Series to cranial ridges in DS9. (The DC Comics premise was disproved much earlier by the appearance of Kor, Koloth and Kang (now with ridges) in the DS9 episode "Blood Oath").
- Klingon Society: FASA Corporation's 1980s Star Trek role-playing game and supplements greatly expanded on Klingon society, enlisting the aid of the late Star Trek novelist John M. Ford. The version of the Klingon society in the 2260s was that of a paranoid society of both "human-fusion" and "Imperial Klingons", complete with sophisticated nomenclatures, a Klingon Emperor, "thought admirals" and an afterlife known as the "Black Fleet." The home planet was known as "Klinzhai". Most of these ideas were superseded in several episodes of Star Trek: The Next Generation (and subsequent productions) which established the Klingon homeworld as "Qo'nos" (also spelled "Kronos") and the Klingon afterlife as Stovokor. Flag ranks in the Klingon fleet have been established (post-FASA) as both generals (such as Martok from Star Trek: Deep Space Nine) and admirals (Star Trek: Enterprise).
The Animated Series
Star Trek: The Animated Series (TAS) was a 22 episode set of animated adventures of the Enterprise crew, which aired originally on NBC from 1973-1974. It featured the reappearance of popular characters from the original series, including Harry Mudd and Cyrano Jones, and speculates on what happened to them after they were last seen in live-action. Some Star Trek novels and comics have utilized characters that were only ever seen in the animated series, most notably Arex and M'Ress. It has been suggested by fans that these stories took place during the fourth or fifth year of Kirk's original "five-year mission." Arguably, the most-debated element of TAS is the introduction of Robert April as the first captain of the Enterprise NCC-1701.
From the show's debut up until the end of the first season of Star Trek: The Next Generation, TAS was considered part of Star Trek canon. Then, from the end of the first season of Star Trek: The Next Generation on May 16, 1988 (when all licenses for Star Trek spin-off fiction were renegotiated) up to June 27, 2007, TAS was "decanonized". However, on June 27, 2007, Star Trek's official website incorporated information from TAS into its library, recanonizing it.