Star Trek's Borg Queen has remained a controversial character since her introduction in Star Trek: First Contact. 1996's First Contact was the second of four films starring the cast of Star Trek: The Next Generation, and the plot revolved around Captain Jean-Luc Picard and crew traveling back to the year 2063 to stop a group of time-traveling Borg from preventing humanity's first contact with the Vulcans. This group of Borg included the Borg Queen, who served as the main antagonist. The Queen was created by First Contact writers Brannon Braga and Ronald D. More in an attempt to adapt the Borg into a more interesting villain for the big screen.
Braga and Moore felt that, while the Borg as a whole worked well on television, their zombie-like nature and lack of a singular identity made them less compelling as the villains of a feature-length film. The writers found it simpler to invent a central antagonist with whom other characters could interact, and so the Borg Queen was created to accomplish this. The Queen was also an attempt to expand on the comparison between the Borg and an insect colony. Much of the language used to talk about the Borg, such as the term "drones" or the concept of a hive mind, was derived from the colony structures of bees or ants, so the addition of a "queen" figure seemed to make natural sense.
Unfortunately, when Star Trek: First Contact premiered, the Borg Queen quickly became a controversial figure among fans. Much of the criticism surrounding the Queen stemmed from the fact her existence had never been mentioned previously, despite the Borg having been a well-established Star Trek villain for years. Many also felt that the idea of a Queen changed the fundamental nature of the species, who did not make decisions based on any singular input. Although the Queen was still connected to the Borgs' collective consciousness, First Contact showed she possessed much more individuality than any average drone, a concept the Borg were supposed to reject. Finally, no satisfactory explanation for the Queen's necessity was ever given during the sequel.
The Borg Queen was killed at the end of First Contact, but her subsequent inclusion in four episodes of Star Trek: Voyager did nothing to clear up any of the controversies. The Queen had originally been played by Alice Krige but was recast and played by Susanna Thompson for three out of her four Voyager appearances. This could have explained her return from the dead, as it could have been argued Thompson's version was a new Queen created after the old one was killed. However, Voyager's series finale, "Endgame", saw Krige reprise her role without any explanation, further adding to the confusion. Voyager also continued to be vague about the Queen's backstory or role within the collective, although if anything the show gave her more individuality than First Contact did, distancing her even more from the established Borg mythos.
While Star Trek is generally good about keeping up with its own continuity or providing explanations for changes, the Queen's backstory remains one of the few things that has never given a satisfactory explanation. Since her appearances on Voyager, the Queen has not been included in any other series or movie, but with the recent renaissance of Star Trek content, it is possible she could return, maybe in Star Trek: Picard which has already done some storylines about the Borg. If that happens, perhaps Star Trek will see fit to finally flesh out the Borg Queen as a character.