Q is a very powerful entity who first introduced himself to humanity by appearing on the bridge of the Enterprise‑D, commanded by Captain Jean-Luc Picard. With a snap of his fingers, Q has the power to change his form, create objects out of thin air, transport people and objects around as he chooses, create elaborate fantasy worlds... practically, he can do anything and everything. Q claims to be omnipotent, and while he is indeed very powerful, his omnipotence is still a matter for debate. He and the other Q entities reside in the Q Continuum, or as Q describes it, the “limitless dimensions of the galaxy in which we exist”.

Q as the Sheriff of Nottingham (2367)

When he first appears to Picard and his crew in TNG 1x01/02: Encounter at Farpoint, he puts humanity on trial for being a “savage, child-like race”, and says that he will not allow humans to travel further into space unless they can prove themselves. Picard manages to satisfy Q on this maiden voyage, but Q says he will be watching. For the rest of The Next Generation, as well as some appearances in Deep Space Nine and Voyager, Q essentially plays the role of Loki, the God of Mischief. He often toys with the crews of Starfleet ships and stations, putting them in silly situations just to test their reactions. One of his most notable games involved putting the senior staff of the Enterprise‑D in a re-creation of Sherwood Forest, forcing them to play out the roles of Robin Hood and his merry men in TNG 4x20: Qpid.

Make no mistake, though: Q is also very dangerous. He was responsible for introducing Picard and crew to the Borg in TNG 2x16: Q Who, making the nemesis aware of humanity far too early, and nearly causing the destruction of the Enterprise‑D. He also seems to have a need to teach “lessons” to humans, once appearing as “God” to Picard, and giving him an opportunity to change his own past, in TNG 6x15: Tapestry.

While there are an unknown number of other members in the Q continuum, they are not as well-known for their interference and hijinks with the human race like the one Q we've come to know and love. The other Q we've met include “Quinn” from VOY 2x18: Death Wish, “Miss Q” from VOY 3x11: The Q and the Grey, and “Q Jr.”, the son of Q and Miss Q, from VOY 7x19: Q2. Their names are all unofficial and made for the convenience of distinction, even though each of them normally just goes by “Q”. There was also Amanda Rogers, a young woman who – unbeknownst to her – was the daughter of two Q parents, in TNG 6x06: True Q. There have been a few other Q seen in various episodes, but the rest were mostly just bit parts. Oh, also, they all seem to enjoy donning Starfleet uniforms whenever they visit, even though they obviously aren't members of Starfleet.

In the 1967 Original Series episode TOS 1x18: The Squire of Gothos, Kirk and his crew are toyed with by a mischievous and powerful being called Trelane. Trelane's powers seem very similar to Q's powers, as does his impish behavior, but Q would not be introduced for another 20 years, in the 1987 TNG premiere, TNG 1x01/02: Encounter at Farpoint, and, indeed, the writers had not even conceived of Q at the time they wrote “The Squire of Gothos”.

However, in 2025, the Strange New Worlds episode SNW 3x02: Wedding Bell Blues would retroactively establish Q as Trelane's father. Now, in-universe, things are a little confusing, especially since the Q entities exist outside of the timeline as we know it. SNW's “Wedding Bell Blues” takes place in 2261, followed by TOS's “The Squire of Gothos” in 2267, and then Q appears to Picard in TNG's “Encounter at Farpoint” in 2364. After all that, in VOY 3x11: The Q and the Grey which takes place in 2373, Q mates with another Q to create a child, which Q says has “never been done”. The resultant offspring of this union (“Q Jr.”) is not the same person as Trelane, according to Strange New Worlds showrunners, so it's a little unclear exactly how, where, and why Trelane came into existence. Amanda Rogers' existence would also seem to contradict Q's assertion that the mating of Qs has “never been done”. In “Wedding Bell Blues”, Trelane says he is 8020 years old, which suggests that he came into existence in 5760 BC, but that is assuming that he experiences time in the same way that we do.

Although Q had visited other Starfleet officers, including Janeway and Sisko, he always seemed to have a particular fascination with Jean-Luc Picard. This would become evident when Q pays a visit to Picard in 2401, thirty-seven years after their first meeting. Seeing that Picard had aged, Q also made himself appear aged as a favor to him (and – let's be honest – so the show could avoid costly de-aging CGI). In this time, Q appears in order to take Picard on a bit of a wild adventure so that Picard can learn to forgive himself for a traumatic childhood event that has haunted him for years. Q admits that he's done this simply because he likes Picard. This story is the primary focus of Season 2 of Star Trek: Picard.