Several characters within the Star Trek franchise, primary and secondary, often made crossover appearances between one series and another. This included appearances of established characters on premiere episodes of new series, a few long-term transfers from one series to another, and even crossovers between Trek films and television. A few crossover appearances, such as that of Spock on The Next Generation and the time-travel of the crew of Deep Space Nine to the era of The Original Series were especially lauded by both fans and critics. Appearances in series premieres After The Original Series, at least one character from an earlier series appeared in the premiere episode of each new series. These were the appearances of most of the Original Series main cast in "Beyond the Farthest Star", the first episode of The Animated Series; Leonard McCoy in "Encounter at Farpoint", the first episode of The Next Generation; Captain Jean-Luc Picard and Miles O'Brien in "Emissary", the first episode of Deep Space Nine; Quark and Morn in "Caretaker", the premiere of Voyager; Zefram Cochrane (from the original series episode "Metamorphosis" and the film Star Trek: First Contact) in "Broken Bow", the premiere of Enterprise; Sarek in "The Vulcan Hello", the first episode of Discovery; Sylvia Tilly in "Runaway", the first episode of Short Treks; Jean-Luc Picard and Data in "Remembrance", the first episode of Picard; NOMAD (from the original series episode "The Changeling") in "Second Contact", the premiere of Lower Decks, and Nyota Uhura in "Strange New Worlds", the premiere of Strange New Worlds. Long-term transitions Two long-term transitions were the transfer of Worf and Miles O'Brien from permanent characters on The Next Generation to permanent characters on Deep Space Nine. Worf stayed on The Next Generation until its conclusion, then transferred from the start of season 4 of DS9. Chief O'Brien had appeared in fifty episodes of The Next Generation, but only gained opening credits billing on DS9, in which he appeared in almost every episode of all seven seasons. While not seen as often as Chief O'Brien, his wife Keiko O'Brien also transitioned as a series regular guest star from The Next Generation to Deep Space Nine, bringing their daughter Molly. Miles O'Brien reprised his Next Generation role in that series' finale "All Good Things...". Episodes and films focused on crossovers Television-to-television crossover An especially significant crossover is Spock's appearance on the two-part Next Generation episode "Unification". Spock