A lirpa is a Vulcan weapon consisting of a wooden staff a little over a meter in length, with a semicircular blade at one end and a metal bludgeon on the other.

Geneviève Bujold was originally cast as Captain Janeway but dropped out on the second day of filming.

The Rigellians were a species of intelligent turtles. According to information obtained by Doctor Phlox, they are believed to have four or five genders.

Keeler was supposed to die in an accident that was prevented by McCoy when he stumbled through the time portal. Instead, Keeler started a pacifist movement, causing the United States to delay its entrance into World War II, allowing Nazi Germany enough time to develop a nuclear weapon and win the war. In order to undo the damage to the timeline, she has to die.

Odo is a member of a shapeshifting race called Changelings. He uses his unique abilities to maintain security on the DS9 station and, later, aids the Bajoran people and the Federation throughout the Dominion War against his own people, the Founders.

Benjamin Sisko and Jadzia Dax are the first to make contact with the wormhole and its creators, noncorporeal beings known as the Prophets. It is they who provided Orb-like energy artifacts to the Bajorans that became the basis of Bajoran religion.

Phasers are common particle-beam weapons first seen in the original Star Trek series.

Thalaron radiation, even in small amounts, petrifies living tissue almost instantly. Its properties allow its range and area of effect to be precisely controlled, from encompassing a single room to engulfing an entire planet.

The Kazon an aggressive warrior species from the Delta Quadrant, were divided into eighteen different sects. Each sect had possession of different natural resources over which the sects fought each other.

In "Mirror, Mirror", the Federation has been replaced by a brutal Terran Empire in which officers ascend in rank by assassinating their superiors, uniforms are more revealing, sidearms are standard issue (as well as daggers for officers), and senior officers routinely torture subordinates.