Dragonriders of Pern

Pern, an isolated world with no useful resources, seemed like the ideal place for people tired of technology to establish a pastoral utopia, until Thread started falling from the skies. An alien fungus that could devour a cow in seconds had not been part of the plan. Rather than permanently resort to technological measures, the colonists used genetic engineering to create dragons, a solution compatible with their principles since, like the spaceships that had brought them to Pern, it was technology they could use once, then discard. Using planes to fight Thread would meant living in an industrial society capable of supporting them; dragons could be supported by the idealised medieval society the settlers had wanted. There's also the matter that they'd been warned the planet's resources were "negligible" - there's insufficient metal and fuel for such an industrial society, wanted or not.

The first Pern story, Weyr Search, was published in 1967. Anne McCaffrey kept writing them for another forty years, though later in collaboration with her son.

Most of the books take place over two thousand years after Pern was first settled, beginning when Thread has been absent for 400 years, ever since most of the dragon riders mysteriously disappeared. Only a handful of people still believe Thread was ever real, and there aren't enough dragons left to fight it if it should return, which it is due to do any day now. Fortunately, it turns out that dragons aren't just fire-breathing telepathic teleporters; they can also Time Travel. The heroine travels 400 years into the past, and brings forward the missing dragon riders, creating a Stable Time Loop.

Subsequent books dealt with the culture clash between the old-fashioned time-displaced dragon riders and the people they had come to save, and with the gradual rediscovery of technology, which led to the unearthing of the original spaceship, and a final end to Thread. There are also several prequels, describing how various aspects of Pern society came to be. Some of the books overlap with each other, covering the same events but following different characters.

The first books had a Fantasy feel, with a few Science Fiction trappings, but later books have moved into Fantasy That Wants to Be Science Fiction territory.

There was also a board game from Nova Game Designs. -

These books provide examples of:

 * Ace Pilot: McCaffrey based her dragon riders' personalities and physical characteristics on real-life fighter pilots.
 * Action Girl: Female dragonriders in general -- Moreta, Sorka, and Mirrim, in particular.
 * Adam and Eve Plot: Averted in the short story "Rescue Run".
 * AI Is a Crapshoot: Averted with AIVAS, who is basically an anti-HAL. Not only does he help free Pern from thread forever, he commits suicide afterward so he won't be a bother to anyone.
 * Alien Blood: Pernese native animals have green, copper-based blood.
 * Alien Sky: The Red Star, of course, but Pern also has two moons. Plus, Pern is far enough away from Earth that the night sky would look very different, with none of the familiar constellations.
 * Aliens Made Them Do It:
 * Dragon mating has a profound psychic effect on nearby humans, particularly their bondmates, making a sexual union between their riders near-compulsory. Weyr culture has adapted to this situation, so permanent relationships among dragonriders are rare. However, a rider's preference can influence his/her dragon's choice of partner -- witness the fact that Mnementh and Ramoth always mate despite the competition from dozens of other bronzes.
 * It's noted in Dragonseye that the riders don't necessarily pair off as the dragons do, but all that needs to happen is that the rider stays near their preferred partner during a mating flight. One character in the book notes that "there are plenty of people interested" in participating when a mating flight is in progress.
 * Fire lizards have a similar effect on their humans, although not as compelling. Still, if you own a gold and someone near you owns the only bronzes in the vicinity, and she decides to have a mating flight...you'd better like each other pretty well. In several cases, such as Menolly and Sebell, this leads to a Relationship Upgrade.
 * Alphabetical Theme Naming: Dragons name themselves at Impression, always with a name that ends in -th: Faranth, Ruth, Mnementh, etc. Why they all seem to hatch instinctively knowing to do this is not explained or even brought up.
 * Author Catchphrase: McCaffrey has a name, "Johnny Greene", or "J.G.", that she likes to insert into most of her works. Jayge is an example.
 * Bad Moon Rising: Well, technically it's a planet, but the Red Star definitely counts.
 * Best Served Cold: Lessa was ready to wait ten years disguised as a menial servant to take revenge on the man who slew her entire family. During this time she turned Ruatha, one of the wealthiest Holds, into a complete ruin through simple sabotage and slight telepathic emotional adjustments, and manipulated F’lar into a duel with Fax to make him pay. She was only ten years old when this started.
 * Blind Jump: Going between without a destination firmly in mind will cause the dragon and its passenger(s) to never emerge, which is fatal. Poorly imagining one's destination can result in a Tele Frag. Conversely, imagining aspects of one's destination too well can result in accidental Time Travel. This is all covered in the extensive training given to young dragonriders, with the grisly examples of those who didn't pay attention in the past serving to drive the lessons home.
 * Bond Creatures: Both dragons and fire lizards, since the former are descended from the latter.
 * A Boy and His X: Dragonriders and their dragons; at various points, people in general and their fire lizards.
 * Brainy Brunette: Lessa.
 * Breath Weapon: Dragonfire.
 * Broken Bird: Lessa. She gets better. Menolly may also qualify.
 * Call a Rabbit A Smeerp: Runnerbeasts and herdbeasts, sort of. While they are related to horses and oxen (and are described as looking similar), they were significantly genetically engineered by the original colonists, so they're probably a different species, technically.
 * Can't Live Without You: Once a rider dies, the dragon normally commits suicide post-haste. Moreta's queen is temporarily tethered by her mothering instinct for the eggs she just laid, but suicides as soon as they hatch. Riders whose dragons die also frequently suicide; those who don't, such as Lytol, remain somewhat shattered for the rest of their lives.
 * Charm Person: Part of Lessa's Psychic Powers manifest as a weak form of this.
 * Chilly Reception:
 * Menolly is accepted by almost everybody in Harper Hall...but the ones who object to her presence make her life hell. A rare example of the protagonist not winning everyone over; instead, she settles for getting her own back.
 * Piemur's example is worse: after his voice breaks, he's sent to become a drum apprentice until his voice stabilizes. However, he's also made Master Robinton's apprentice, which often involves being sent on very confidential missions. Determined to prove that he's not just a joker and a slacker who coasts by on natural talent, Piemur makes a decision to stop playing around and start working -- and the other drum apprentices, who were expecting the joker, don't take it well, especially when Piemur learns drum measures at a speed most of them probably couldn't match. His going on said missions, including one to a Gather at Igen Hold and, as far as they knew got a free day because of a Hatching at Benden Weyr, just makes it a lot worse . Further problematic was the Journeyman who was generally on watch never believed him on any matters.
 * Colour-Coded for Your Convenience:
 * Dragons' colors denote gender, size, and rank, exactly as their fire lizard ancestors. Gold = Queens, the dominant females and the primary egglayers; Bronze = the largest and dominant males, ridden by wingleaders; Brown = smaller and weaker males, tend to be ridden by wingseconds; Blue = the smallest, fastest, and least intelligent males; Green = the smallest, subordinate females, who are typically infertile due to firestone consumption.
 * The various Holds and Crafts have traditional colors and shoulder knot patterns that denote rank and affiliation. About the only color ever consistently mentioned is that Harpers are associated with a light shade of blue known as "Harper Blue."
 * Comet of Doom: The Red Star, although it's technically not a comet, serves the role plot-wise.
 * Cool Pet: Fire lizards.
 * Corrupt Bureaucrat: Chalkin, Lord Holder of Bitra in Dragonseye, who refuses to believe that Thread will return and won't take the necessary precautions to protect his people. And that's just the tip of the iceberg of the things he does.
 * Culture Clash: Between Weyr, Hold, and Craft. Their traditions have diverged sharply over the centuries and frequently come into conflict in the main storyline. Similarly, a major conflict arises between the Oldtimer Weyrfolk who are brought forward in time by Lessa and the more "modern" Weyrfolk under F'lar's command.
 * Death By Childbirth: Happens to Jaxom's mother, and is generally a risk in a low-tech, feudal society.
 * Death World:  pay a visit to the Red Star and come back near-dead and skinless from the corrosive, unbreatheable atmosphere.
 * Despair Event Horizon: The death of a dragon or its rider will send the living member of the pair into despair or insanity. If the rider dies, his dragon will invariably commit suicide by going between. If the dragon dies, the rider may become Ax Crazy, suicidal, an Empty Shell, or all of the above.
 * Development Hell: The Live-Action adaptation has been stuck in it since 1995.
 * Domestic Abuse: F'lar is very rough with Lessa at first; he gets less so as their relationship matures.
 * Don't Make Me Take My Belt Off: Menolly's father beats her in this manner for the grave sin of improvising her own music.
 * While F'lar doesn't go quite this far, he has a tendency in the earlier books to shake Lessa when she upsets him.
 * Dramatis Personae: Used in most of the early Pern novels, then quietly dropped later.
 * Dragon Rider: One of the Trope Makers.
 * Driven to Suicide: Happens to riders whose dragons die, and vice versa.
 * Drowning My Sorrows: Even decades later, Lytol drinks to unconsciousness after a dragon dies to numb the pain of losing his.
 * Robinton is also overly fond of drink, and has been ever since his bride Kasia drowned on their honeymoon.
 * Due to The Dead: Centuries after she sacrificed her life to save Pern, Salla Telgar's body is brought down from space and given a very elaborate ceremonial funeral, including the coffin being borne by queen dragons.
 * Menolly is first introduced in Dragonsong as singing the funeral elegy for Petiron.
 * Empty Shell: If a rider who loses his dragon does not commit suicide, he or she is frequently left as this. The quintessential example is Kylara, who is left almost catatonic when her queen dies.
 * Lytol manages to avert this. While he never gets over the pain of losing his dragon, he presses on through life by engaging in other pursuits. First by being a Weaver, then by dedicating himself to making Ruatha Hold prosperous again for his ward Jaxom, whom he treats as a son.
 * Enemy to All Living Things: Thread eats its way through anything organic -- being tied out during threadfall is the single most dire punishment that a criminal can be sentenced to. Drowned Thread OTOH (Thread can't survive in water) is a rich food source for marine life. While the rest of Pern suffers due to Thread, fish and other sea animals thrive.
 * Estrogen Brigade Bait: Robinton, in-universe. In one scene Piemur is torn between amusement and frustration that his elderly mentor distracts all the ladies from him.
 * Eternal English: Over 2500 years on Pern have introduced a lingual shift despite the best efforts of the Harpers. However, the shift is not so severe that, allowing for the loss of context, they cannot understand the language of their ancestors. Documents and recordings from the colonists are still understandable to modern characters (though some of the context has been lost). After being unburied, AIVAS is able to rapidly adjust its language to make itself understood. The dolphins underwent a similar linguistic shift, mostly becoming simpler and filled with abbreviations (for instance, the "blood fish" that attach themselves to the dolphins' undersides like leeches became "bluufis").
 * Executive Meddling: In a rare inversion of the typical trope, a studio executive actually stopped production of a TV series based on the novels a few days before shooting because of Adaptation Decay.
 * Fanwork Ban: The author was legendary for her adamant opposition to fanfic, and while she permitted roleplaying games, attempted to exercise editorial control over what could be done even in people's individual RPs. (The latter was less successful; even today, "pink dragons" are something of an in-joke in the fandom.)
 * Fantastic Recruitment Drive: When the dragonriders go on Search, they seek young men and women with latent telepathic abilities, able to bond with dragons.
 * Fantastic Time Management: Used mostly-trivially by Jaxom, and far more seriously by Moreta.
 * Fate Worse Than Death: Most pernese consider being banished from a hold a harsher punishment than execution, since they automatically assume the condemned is going to be eaten by thread. Several characters learn to survive holdless simply by hiding in caves. Menolly notes that most of the time very little Thread actually gets to the surface thanks to the dragonriders.
 * Losing their bondmates is this for dragons/dragonriders. Riders whose dragons die usually commit suicide. Dragons whose riders die always commit suicide.
 * Feminist Fantasy: Well, the installments written in the 1960s and 1970s were, by the standards of the time. The goalposts have been moved considerably since then. (See Victim Falls For Rapist, for one thing.)
 * First Girl Wins: Robinton's short-lived wife Kasia still haunts his dreams. When he becomes involved with Silvina, he offers to marry her when she informs him that she's pregnant. She refuses (gently) because it's Kasia's name he still says in his sleep; he never recovers from losing her.
 * Florence Nightingale Effect:
 * Jaxom and Sharra's relationship begins this way, after she treats him for Firehead Fever.
 * When Lessa is treating F'lar's knife wound, she can't help but notice his manliness.
 * Free Love Future: The Weyr culture is highly liberated due to the nature of dragon/rider relationships; dragons mate with whom they choose and their partners are compelled to do the same. Children are fostered and raised by the Weyr as a whole to avoid attachments to any particular parent, given their high mortality rates.
 * Fun With Acronyms: Pern (Parallel Earth; Resources Negligible), and AIVAS (Artificial Intelligence Voice-Address System). Word of God says that Pern is a backronym; McCaffrey came up with the name for the planet a long time before deciding it meant anything.
 * Gender Rarity Value: Applies in this case to the dragons; golds are the least common dragon color and yet the ones primarily responsible for populating the Weyrs. Over the last Long Interval, the Weyr population diminished to the point where there was only one gold alive at any time, making the extinction of the species a real possibility and justifying the taboo against flying golds in combat, something which had not existed in previous Passes.
 * Genetic Memory: There is a very strong implication that fire lizard memory is this; it's hard to imagine any other way that they could remember the events of Landing so vividly two thousand years later. In fact, it's fire lizard memory that leads Jaxom's team to discover the original Landing site, as well as AIVAS.
 * Another possibility that has been implied is that the telepathic firelizards form a weak hivemind, complete with a collective memory. However, the effect is functionally the same.
 * Geographic Flexibility: Travel times around Pern seemingly vary according to the needs of the plot.
 * Get a Hold of Yourself, Man!: When F'lar gets ill in Dragonquest, he starts Wangsting and must be told this by Lessa.
 * Giant Flyer: The dragons.
 * Gosh Dang It to Heck: When not using Pern-specific curses, characters have a tendency to say things like "dratted" or "blasted." There's even "Jays" in Dragonsdawn, mean to be a Bowdlerization of "Jesus." Strangely, in the same book, one character calls another a "gobshite."
 * By contrast, there are quite a few "S-" and "F-bombs" in Dragonsdawn, what with the initial colonists still speaking (future) English.
 * Growing Up Sucks: For Piemur, puberty ends his sheltered life as a boy soprano.
 * Guile Hero: F'lar and Robinton, later Lessa. Also Sebell. It seems that this is one of the traits required to become MasterHarper. Menolly and Piemur to lesser degree.
 * Happily Married: A lot of Pernese couples don't actually marry, but among those who do, there are a number of happy couples. Petiron and Merelan fit this trope, as did Robinton and Kasia (for the few days of their marriage). Even these, who aren't officially married act like this anyway.
 * Heroic Albino: Ruth
 * Hide Your Gays: Half averted. Homosexual men are not uncommon on Pern, and in fact most (if not all) blue riders fit the bill. There is never a mention of homosexual women, however.
 * Horse of a Different Color: Dragons, of course, although real horses and oxen do exist.
 * Hot for Teacher: It takes a while, but Menolly and Robinton finally acknowledge their UST in The White Dragon, although nothing comes of it. Her commitment to Sebell aside, Robinton had recently suffered a heart attack...
 * Huge Guy, Tiny Girl: F'lar and Lessa.
 * Hyperspace Is a Scary Place: Between, the dimension used by dragons and fire lizards when they teleport, is devoid of sensation, airless, and brutally cold.
 * And also apparently prone to causing miscarriages if a female rider is still in the early stages of pregnancy when she goes between.
 * I Thought Everyone Could Do That: Lessa talking to dragons, which gets F'lar extremely angry with her when he had been trying for years to figure out a way to coordinate all the dragons of a Weyr in combat.
 * I Have Your Wife:: How F’lar manages to convince the Holders to cooperate with Benden Weyr after the Long Interval -- he sends dragons to abduct their wives and daughters.
 * Jackie Robinson Story: Menolly becoming the first female Harper in the Harper Hall Trilogy.
 * Well, the first one in a long time. It's been stated that before the pandemic in Moreta's time, which nearly wiped out humans on Pern, that there was far more sexual equality. After that, women reverted to more "traditional" roles because of the need to repopulate.
 * Jerkass: Okay, let's count 'em. Kylara, Lord Meron, Thella, T'kul, T'ron, Mardra, Merika, Masterglasssmith Norist (leader of the anti-AIVAS group), Lord Fax, Lord Chalkin, Yanus (Menolly's father), and more. It seems that every major antagonist character in the series is not merely opposed to the heroes but a complete dick as well.
 * Not just antagonists. F'lar in the first book is something of Jerkass Stu. Subsequent books rebalanced his personality considerably.
 * Mirrim's also a Jerkass, but while she's on the good guy side, everyone acknowledges that she's hard to get along with.
 * Kaleidoscope Eyes: Dragons' and fire lizards' eyes change color according to their mood.
 * Kill'Em All: Todd McCaffrey's solo books.
 * Kill It With Fire: Dragons and fire lizards do indeed breathe fire, although it's the result of a hypergolic gas released when they chew a naturally occurring mineral named "firestone". On foot and in the queens' wing, Thread is fought with flamethrowers, or nitric acid sprayers (colloquially termed "agenothree" in the books -- HNO3, get it?)
 * Knife Nut: Dragonriders don't carry swords, but many are deadly efficient duelists with eating knives.
 * Legend Fades to Myth: In Dragonsinger, we are introduced to the legend of Moreta, the Dragonlady who saved Pern from a deadly epidemic at the cost of her own life. Moreta: Dragonlady of Pern (published at a later date) recounts the actual events that gave rise to the legend.
 * Loads and Loads of Characters
 * Long Running Book Series
 * Lost Colony: The colonists wanted Pern to become this to live peacefully; the later discovery of Thread by a rescue ship mean it's now permanently lost as the entire system is under quarantine.
 * Mad Lib Fantasy Title
 * Magical Abortion: The cold of between is sufficient to induce miscarriage and is deliberately used for this by female dragonriders, who are seldom able to take enough time off for pregnancy. It's either that, suffering accidental miscarriage from riding a dragon all the time, or fostering the kid out as soon as possible.
 * Manipulative Bitch: Lessa, before impressing Ramoth. She gets better.
 * Medieval Stasis: For about two thousand years, Pern was medieval with very little structural/social change. Justified by the fact that most of the colonists' technology was lost or worn out after two hundred years, and the whole "Thread trying to eat everything organic" situation made them more concerned about surviving rather than technological advancement. When this incentive is removed after All the Weyrs of Pern, they begin to reclaim their lost technology with the help of the records and instruction provided by AIVAS.
 * Also justified because Pern was settled by Space Amish who wanted to get away from technology and develop a more agrarian society, though they didn't want to decay quite as far, hard or fast as they did.
 * Mercy Kill: Sometimes administered to badly injured Thread victims, by means of a lethal dose of "fellis", an herbal sedative.
 * Multiple Tailed Beast: Pernese dragons have forked tails.
 * The Napoleon: Lessa
 * Never the Selves Shall Meet: This seems to change at different points in the series. At the start, Jaxom coming close to himself causes incredible exhaustion, and Lessa overrunning herself three times at the same temporal point results in swaying and mumbling gibberish. By the time of Todd McCaffrey's stories, M'hall and Master Harper Zist both talk to their past selves outright with no issue.
 * New Powers As the Plot Demands: In The Skies of Pern, the dragons "discover" their powers of telekinesis. This is not entirely pulled out of thin air; in All The Weyrs of Pern, AIVAS said that dragons should be able to do it, and it was covertly confirmed when the dragons were able to carry huge starship engine assemblies that, despite the lower gravity of the Red Star, they should not have been able to support, even en masse.
 * No Biochemical Barriers: Averted, hard, as the Pernese settlers were armed with advance surveys and the science to clearly identify which local lifeforms were good to eat and which weren't, and they wouldn't have tried to settle Pern in the first place if the atmosphere wasn't breathable, etc. They also brought a lot of Earth lifeforms and conducted extensive experiments to determine compatibility, modifying genes where necessary -- incidentally, this is why there are no bees or turkeys on Pern.
 * Or coffee. In Dragonsdawn it's mentioned that for some unknown reason coffee had proven unable to be adapted to growth on any planet other than Earth. On Pern, this leads to the development of a substitute made from the ground bark of a native tree, a drink that becomes known as klah.
 * No Blood Ties: Although bloodlines are acknowledged, it is common practice among Weyrfolk to foster their children to avoid maternal or paternal attachments; this lessens the trauma when riders are lost fighting Thread.
 * No Mere Windmill: Type B. When F'lar (and his father before him) warns the political leaders of the soon-to-begin Ninth Pass about the return of Thread, they refuse to believe him, until it starts dropping on their heads of course.
 * Not Good With People
 * Old Retainer: Rannelly, for Kylara.
 * Our Dragons Are Different: Another Trope Codifier.
 * Outgrown Such Silly Superstitions: The Pernese colonists were specifically selected for their lack of susceptibility to religion. Throughout the entire series, God is not mentioned once. On the other hand, it's mentioned in Dragonsdawn that much of the Judeo-Christian Bible consists of plain common sense that the Pernese hold to "without any trace of fanatical devotion," and Aivas considers the Bible to be "the greatest book ever written by mankind."
 * Parental Abandonment: Lessa (parents murdered by Fax), Jaxom (mother died in childbirth, father was the aforementioned and unlamented Fax), and others.
 * Parental Incest: Steve Kimmer, in Rescue Run.
 * Patronymic: Somewhat turned on its head. Many (though not all) Pernese children, particularly those born in the Weyrs, are given names which are meshes of the names of their father and mother. For example, F'lar's birth name was Fallarnon, after his father Fallon and mother Larna; his half-brother F'nor was Famanoran, after father Fallon and mother Manora. Sometimes other people's names are used in the convention, such as Menolly and Sebell's youngest son Robse (the first part of his name being in honor of Robinton).
 * Pride: Lessa, full stop. She is completely willing to let dragons battle with each other, because she feels insulted.
 * The Plague: The plot of Moreta and Nerilka's Story, as well as Dragonsblood.
 * Planetary Romance
 * Poor Communication Kills: Early on, Lessa and F'lar spend a lot of time not telling each other things. They get better.
 * POV Sequel: Moreta and Nerilka's Story. There's also a multitude of books that take place around the beginning of the Third Pass and near the middle of the Ninth that play with this; while they show many of the same events from different perspectives, they also have a tendency to cover time further back or forward than each other instead of taking place entirely simultaneously like a true POV Sequel.
 * Properly Paranoid: F'lar, about Thread.
 * Psychic Powers: It is said that all dragonriders are at least slightly telepathic to the extent required to communicate with their dragons. The dragons themselves, as well as their smaller cousins the fire lizards, are telepathic with each other and their riders. Lessa is a rare example of someone with the ability to affect other humans, but this was quietly downplayed as a plot point after being introduced.
 * Punctuation Shaker: Justified; all male Weyr riders have their names ritually contracted after Impression, to make shouted communication easier during Threadfall. For example, F'lar was born Fallarnon. Losing your dragon (and surviving) sometimes revokes this, as Lytol was of course L'tol when he was a rider, but went back to a non-hyphenated name (though not the same as his original name) after his dragon died.
 * Some humor comes from the difficulty in figuring out what Jaxom's rider name ought to be after he accidentally impresses Ruth; the situation is resolved by allowing him the unique privilege of being a dragonrider and Lord Holder.
 * Random Teleportation: One of the obvious risks of a poorly visualized trip between.
 * Rape and Switch: Anne McCaffrey had an infamous opinion that anal rape releases hormones that turn men permanently gay; according to Word of God this would canonically apply to male greenriders if one who wasn't already gay was chosen. This is never stated in the text, and as it makes very little sense to most people who are not Anne McCaffery, it's usually ignored.
 * Real Men Hate Affection: Petiron's attitude toward his son Robinton is a good example. Whether Petiron just didn't know how to show affection, or felt threatened by the fact that his son was much more talented than Petiron himself was, Robinton as a young boy is constantly looking for affection his father never offers. The situation improves as Robinton becomes an adult and is named MasterHarper, upon which Petiron steps down as MasterComposer and exiles himself to a minor holding to allow Robinton to become a leader in his own right. Later on, Petiron redeems himself when he discovers Menolly's talents (and sees her father's attempts to squelch her) and sends her to Robinton for mentoring.
 * "The Reason You Suck" Speech: Robinton delivers three of these: to the Lord Holders in Dragonflight and Dragonquest, and to the Abominators in All The Weyrs of Pern.
 * Reassignment Backfire: A subversion occurs with Petiron, who was assigned to a backwater fishing Hold that just happened to beget one of the greatest musical prodigies in Pernese history, Menolly. Then it turns out that he was assigned at his own request, and that his son is the current Masterharper, Robinton.
 * Rebellious Princess: Nerilka, a Lord Holder's daughter, refuses to obey her Jerkass father's commands and becomes a nurse during the plague.
 * Refused By the Call
 * Retcon: More than once. A lot of plot elements got modified between Dragonflight and Dragonquest, specifically, some of the character names and several aspects of dragon biology. Further, in Dragonquest, there's a specific reference to fire lizards "eating Thread" which is never mentioned before or after.
 * As the "fire lizards eating thread" bit was said by Kylara after her thunder had just been stolen by F'lar, it was likely something that she pulled out of her ass to bring attention back to herself. It worked quite well.
 * In Dragonsinger, which parallels Dragonquest in the Harper Hall trilogy, Menolly's fire lizards, while shut inside the Harperhall refectory during Threadfall, get very excited and are described as making the motions of "licking Thread from the air." This is the only other mention; in later books it's made quite clear that they destroy Thread by flaming it.
 * Rocks Fall Everyone Dies: Todd McCaffrey's books tend to end with the antagonist (and/or most of his cohorts) getting slaughtered.
 * Sapient Cetaceans: The original settlers brought intellectually enhanced dolphins with them, but lost contact in the exodus to the Northern Continent. In the aptly titled Dolphins of Pern, Jayge and Aramina's son Readis becomes the first to reestablish contact.
 * Science Fantasy: One of the classic unclassifiables. McCaffrey has always contended that her books are Science Fiction, not Fantasy. Her reasoning is that everything in the books is (in her estimation, at least), scientifically backed.
 * Science Is Bad: The Pern colony was founded on the principle of rejecting reliance on high technology to solve problems. Millennia later, this sentiment bestirs itself in the form of a violently Luddite group that attempts to sabotage anything related to AIVAS. AIVAS' discovery, however, is what eventually leads to the final end of Thread on Pern.
 * Science Marches On: Millennia in the future of our day, the world of Pern is finally saved with DOS. An AI version of DOS, but still...
 * Sci Fi Writers Have No Sense of Scale: Distances seem to change at the plot's convenience, and either dragons in the Ninth Pass are ludicrously huge (bronzes and golds being much bigger than blue whales) or someone said "meters" when they meant "feet."
 * Sex By Proxy: Thanks to the mental link between dragons and riders.
 * Shoulder Sized Dragon: The fire-lizards.
 * Space Amish
 * Stable Time Loop: All time travel in series either results in one of these, or is the result of one of these.
 * Starving Artist: Iantine, in Dragonseye, is reduced to this on account of the bad weather and political corruption he encounters in Bitra.
 * Succession Crisis: A few of them:
 * A minor one in Dragonflight, where Lessa, Fax and F'lar are all intriguing over who has the right to rule Ruatha Hold. Lessa is the dispossessed rightful heir to Ruatha, Fax is the usurper, and F'lar unseats Fax, but in favor of Fax' son Jaxom rather than in Lessa's favor.
 * In the Harper Hall trilogy, Meron deliberately avoids naming a successor as he's dying (he wants a bloody succession fight to spite everyone,) until Robinton uses reverse psychology to get him to select the son he thinks nobody wants.
 * In All The Weyrs Of Pern, Oterel's death requires the other lords to vote on his successor. Thanks to petty political bickering, they have a lot of trouble getting consensus on the one son who isn't blatantly an idiot or wastrel.
 * Synchronization: Riders and their dragons.
 * Teacher-Student Romance: Robinton and Menolly, but an unusual example. They know they're fond of each other, and after  they both admit that said feelings are not 100% platonic. However, she's involved with someone else, and he is very much in favor of that relationship. So other than that brief recognition and pang, his relationship to her remains teacher / surrogate family.
 * Technician Versus Performer: Petiron vs. Robinton/Menolly.
 * Tele Frag: One of the risks of going between with a poorly visualized destination.
 * Teleporters and Transporters: Dragons and fire lizards are innate teleporters, and can bring passengers with them. This is accomplished by making use of Another Dimension, colloquially termed between, which lacks all sensation and is killingly cold. It is later discovered that they can teleport across interplanetary distances as well as through time, but the amount of time spent between increases with distance travelled (temporally and spacially).
 * Time Travel: An innate, if rarely used, ability of dragons and fire lizards. When travelling between, one must visualize one's destination accurately; apparently, this also includes time references. For example, if you visualize your destination in the morning, that's when you'll get there. It's even got a colloquial term in the story: "timing it".
 * Uncoffee: Klah, which is made from tree bark, started out as the colonists' ersatz coffee, and ended up filling the same cultural niche. It's explicitly stated to contain stimulants and taste exactly like hazelnut coffee. Dragonsdawn explains that coffee and tea plants can't flourish on Pernese soil, so the colonists looked elsewhere for their caffeine needs.
 * Unusual Euphemism: "Shards", "Shells", "Scorch it", and various other oaths are employed by Weyrfolk, mostly relating to dragons or Thread. Makes sense, as there's no religion on Pern, but respect for the dragonriders as saviors from Thread kind of fills a similar cultural role. "Fardling" is their variant of the "F" word. There's an index specifically for these in the early novels.
 * Victim Falls For Rapist: Surprisingly common for what (at least at one time) was considered a work of Feminist Fantasy.
 * F'lar and Lessa definitely count -- F'lar even admits it to himself in Dragonflight.
 * The first time F'nor and Brekke have sex comes across this way to most readers, although there's some debate.
 * Arguably F'lessan and Tai as well, although in that case the only possible rape was triggered by a mating flight.
 * What Could Have Been: In The Masterharper of Pern Robinton is noted to have the ability to speak to (and hear) dragons, leading to his mother actually hoping that he would be Searched by a Weyr in order to get him out of their troubled home. Unfortunately no queens were laying when Robinton was of the optimal age to Impress a dragon.
 * What Measure Is a Non-Cute?: Dragons? Gaze up in awe and go "whoa, cool!" Fire lizards? Gather round and Squee over the pretties. Watch-whers? Chained to a wall as barely tolerated "watchdogs". Although they are shown as capable of friendship and loyalty, and their distant kinship to dragons is mentioned from book one, it is not until the prequels that their origin is revealed -- partially failed experiments in creating a second type of dragon.
 * You Already Changed the Past: There are no Temporal Paradoxes in this universe. If you use Time Travel to go backwards, you had already been there and had done what you did. In fact, several characters use this type of foreknowledge specifically to plan their trips, setting up a Stable Time Loop.