Thank god for Q. Or -- since Q within the Star Trek universe is a god -- perhaps we should say, "Thank Q for Q."

Q is only one of two characters in Star Trek lore who have shown up in all three 24th century Star Trek shows (The Next Generation, Deep Space 9 and Voyager). Curiously, the other character to share this honor is the Ferengi Quark. Star Trek clearly had something about the letter Q... chalked up by fan lore to Gene Roddenberry's fascination with Janet Quarton, the first president of the UK Star Trek fan club.

Regardless, within Star Trek canon, Q is best described as a rogue, Mephistophelean godling. Although he generally means well, as far as that sort of thing goes, Q is usually referred to as "obnoxious", "interfering" and a "pest" by the Starfleet captains who encounter him. No wonder: Every time Q pops in to visit, something generally goes catastrophically wrong.

Q's first encounter with the Federation was aboard the USS Enterprise-D in Star Trek: The Next Generation's premiere episode, "Encounter at Farpoint." Dressed in sumptuous emperor's robes, Q kidnapped the Enterprise crew and dragged them backwards in time, to a post-apocalyptic 21st century court room, where he put them on trial for being a "dangerous, savage child-race." Picard convinced Q that they were ready to explore the stars peacefully, which he somehow managed to do by freeing a couple of cosmic jellyfish from being used as space stations. No, it didn't even make much sense at the time, but Q seemed happy with the results... the first indication within Trek lore that Q was not as dangerous as his god-like powers would first seem to indicate.

Over the course of the next seven years, Q would make eight more appearances on the USS Enterprise-D. Q was the entity responsible for hurling Picard and his crew into the path of a Borg Cube after Picard bragged that humanity was ready for anything. Although the action seemed malevolent at the time, and the Enterprise was almost destroyed, the action ultimately betrayed Q as deeply concerned with the welfare of humanity: If he hadn't warned the Federation about the existence of the Borg before they reached Earth, they would not have been able to successfully repel them.

Q was particularly fascinated with Picard. When Picard "died" because of a malfunction of his artificial heart, Q offered Picard the chance to relive the incident which had caused him to lose his heart in the first place. Picard accepted, but as he changed his life, he realized the event made him the dynamic, courageous explorer of his later years. Ultimately, Picard decided to be stabbed in the heart again, reclaiming his identity and earning a smile and a wink from the mischievous God.

And just as Q appeared in the first episode of The Next Generation, he appeared in the last. In the episode "All Good Things..." Q re-appears to Picard seven years after the Encounter at Far Point, claiming that humanity's trial never ended. He then splits Picard between three time periods (one in 2364, one contemporary, and one in the future when Picard is a doddering old man) and challenges him to solve a temporal paradox that will wipe out all life as he knows it. When Picard eventually solved the riddle, Q congratulated him for being capable of embracing the more advanced concepts of the universe. His last words aboard the Enterprise-D? "The trial never ends."

If there was a captain and a ship that Q found just as fascinating as the Enterprise, though, it was Voyager and Kathryn Janeway. In his first appearance on Star Trek: Voyager, Q appeared to convince Janeway not to give asylum to a renegade deity of Q's race, the Q Continuum. This renegade deity was also named Q.

Janeway's pluck and Voyager's curious situation intrigued him. When the Q Continuum broke out into a civil war a year later, Q reappeared aboard Voyager to pose an interesting solution to the problem: He would mate with Janeway and she would give birth to a half-human Q-ling that would usher in a new era of... well... Q-ness. Janeway refused, but she managed to help Q end the intergalactic Ragnarok anyway, non-carnally. As a result, Q showed Janeway a shortcut to bring Voyager back to the Alpha Quadrant, shaving three years off their journey. His offer was also incidentally beneficial to the Federation -- by doing so, Q directly (and purposefully) but the crew of the Voyager in the path of a Transwarp Hub that was being used by the Borg to mount a full-scale invasion of the Federation, and which Voyager succeeded in destroying... after using it to get home.

Q has many incidental appearances in spin-off media: He's a popular character both among Trekkies (who appreciate John de Lancie's impish relish in playing the role) and among Trek's producers (who appreciate John de Lancie's impish relish in getting a paycheck). In truth, he's Roddenberry's alien archetype at its most tedious: Omnipotent, moralizing and bombastic. But John de Lancie made what could have been a dreary mouthpiece for Roddenberry's thoughts on mankind's failures into a charming Falstaffian rogue. Without him, Star Trek would never have had a 24th century.