A Form You Are Comfortable With: The kids never find out what the Ellimist really looks like, as he usually takes a humble, benign human shape. The reader does get a vague and incomplete description of Ketrans in The Ellimist Chronicles, and the Ellimist says, after his ascension, that he chooses the humble form of a mere Ketran (in contrast to the terrifying, monstrous form Crayak chooses.) The cover of The Ellimist Chronicles most likely shows the Ellimist's favored form.
Book 41, "The Familiar" centers on a Bad Future where the Yeerks have conquered Earth—Marco is Visser Two's host and is in charge of Earth, Cassie is a jaded terrorist and member of a resistance led by Tobias, who uses a morph of Ax, Ax is a Yeerk general that conquered the Andalite homeworld, and Rachel is crippled. The only free member is Jake, who tries to figure out what's going on. Even in-universe the world doesn't make sense though, such as how Cassie at one point uses thought-speak while human and Tobias stating that Jake is supposed to be dead, and it's revealed to be All Just a Dream. As Jake awakens he hears an entity speaking that humans require "more study", implying it was a vision from the entity. Nothing in the book ever comes into play in the rest of the series and the mysterious entity is never mentioned, though it is known that it isn't the Ellimist or Crayak.
A few off-hand references are made to the Yeerks having some presence on the Andalite homeworld, but this never developed into anything and by her own admission Applegate just forgot about it.
Absurdly Sharp Claws: Andalite tail-blades are incredibly precise and demonstrably sharp enough to cut metal and lop off limbs.
The Ace: In-universe, Jake is seen as this. Whether or not he actually qualifies is a little more ambiguous.
Rachel, a beautiful, popular girl with an indomitable spirit, a star athlete and a genius student (she gets a national award for academic excellence at one point) could've easily become this if she hadn't let the war turn her into a violent Blood Knight (although it's worth noting that she still became the best fighter amongst the Animorphs...).
Achilles' Heel: The two-hour time limit for the Animorphs. The Yeerks also have a weakness: they need to absorb Kandrona rays every three days.
Achilles in His Tent: Jake, for a couple books in the final story arc. Though he's actually angry at himself, as he failed to keep his parents from being infested. In his mind, he's unfit to lead. When he does come back as leader, his personality has changed considerably...
Action Girl: Rachel, most prominently, verging on Dark Action Girl by the end. Cassie as well; she doesn't have Rachel's Blood Knight tendencies, but she can more than hold her own in combat. Loren in The Andalite Chronicles is especially impressive given that she has no special powers.
Adults Are Useless: Eventually averted once they find adults they can trust not to be infested. This ends in them getting the support of the government and becoming much more effective.
Affably Evil: The original Visser One who uses Marco's mother as a host comes across as a friendly Reasonable Authority Figure compared to Visser Three, although that's not saying much. In one of the prequel books, Visser Three himself seemed to fit this when he was younger/in his earlier host body, prior to becoming an Evil Overlord.
Alien Abduction: The Skrit Na abduct and experiment on humans for unknown reasons.
Aliens Are Bastards: Fairly obvious with the Yeerks, but the Andalite case is far more interesting. In the beginning of the series, kids look up to their erstwhile saviors, the great and glorious Andalites, and are counting on them to swoop in and save the day. It becomes increasingly obvious, however, that Andalite military command couldn't care less about humans. In the end, their strategy for for winning the war was to bombard Earth from orbit to take out as many Yeerks as possible.
Alien Sky: The Andalite homeworld has a red and gold sky with multiple moons. The Yeerk homeworld has a green sky and constant thunderstorms. In The Andalite Chronicles, Loren, Elfangor, and Sub-Visser Seven create a weird hybrid of their respective homeworlds, and the sky is a patchwork of three different kinds of sky.
Aliens Steal Cable: And record every channel! The Andalites apparently show TV programs like the news and MTV in school as part of learning about humans. At one point Ax, apparently not content with free-to-air TV, actually does steal cable.
Mostly averted, with similarities generally being more by analogy, such as Andalite vs. Earth grass despite theirs coming in shades such as red.
The Yeerk planet is completely different and unpleasant. Fittingly.
All-Powerful Bystander: The Ellimist and Crayak. If one of them tries to do something, the other will fight right back to counteract them. Last time they went all out, a good chunk of the galaxy was destroyed. Now they mostly just sit back and play Chessmaster.
All Therapists Are Muggles: Cassie tries but mostly the characters are on their own. Marco lampshades the impossibilities of telling a professional therapist about their problems: "Hello, Doctor Freud? My dad's thinking about remarrying. See, he thinks my mom is dead, but she's not. She's actually a slave to an alien race trying to take over the planet. And did I mention that I'm fighting this alien invasion myself? That I do it by turning into animals? Say what? What size straitjacket do I wear?"
All Up To You: Cassie has two or three of these. Take, for example, #29, The Sickness, in which everyone gets a fever but her; and #44, The Unexpected, in which she gets separated from the others on an airplane flight to Australia.
Alternate Continuity: The Alternamorphs series featured two books, The First Journey and The Next Passage. They were structured in the form of a Choose Your Own Adventure type story. In the first book, the reader became part of the group that gained the morphing power from Elfangor and joined the Animorphs on their first adventure. Upon completion of this, the story continued with an adventure involving a Sario rip (rip in time). The second book involved elements from two different Animorphs stories from around the midpoint. However, the books were structured in such a way that only a single set of possibilities allowed you to continue the story. Perhaps, for this reason, the series never really caught on, has been largely forgotten, and was discontinued after the second book.
Megamorphs #3: Elfangor's Secret and Megamorphs #4: Back to Before both play with this. In #3, they follow Visser Four with the Time Matrix and experience him changing the outcome of battles and other historical events to his benefit. In #4, the Drode lets Jake see what it would have been like if they had never been given the morphing powers.
#41 The Familiar is also an example: Jake goes to a potential future.
Predating all these examples is #07 The Stranger. Animorphs was fond of this trope.
The Howlers are the army of doom of Crayak, a malevolent god. A hive-mind, they've destroyed countless worlds without hesitation. The twist? They never knew killing was wrong, or that other races didn't like to be killed. They are perpetually innocent, like small children, and killing is their "game". Their collective memory is culled when necessary to preserve their naivete. Then Jake manages to sneak a memory of him kissing Cassie into their hive mind. They then try to kiss everything in sight rather than massacre it.
Hork-Bajir: Eight-foot walking razor-bladed lizardmen, who appear bred purely for combat. Turns out they're Gentle Giants, vegetarians in fact (the blades are used to harvest bark), used as host bodies by the Yeerks for their brute power. Which brings us to?
Yeerks: Literal brain-slugs who control your mind. But the Yeerks were largely pushed towards conquest by a hatred of their standing in the galaxy. In their natural state, they're 2-inch slugs, doomed to a blind, drab existence unless they take host bodies. Most, at least the ones we see on Earth, have embraced conquest, but there are a few who cooperate with the host rather than completely controlling it, and even fewer who are actively against the invasion. They're Often Chaotic Evil, but not always. Even those who have embraced the imperialist philosophy don't see themselves as evil, just doing what they naturally do (you don't think of yourself as evil because you kill and eat pigs, do you?); this mindset has been drilled into them with Yeerk Empire propaganda since birth.
Then there's the Taxxons, who turn out to be intelligent beings trapped in bodies that are slaves to hunger, to the point that one recently disemboweled Taxxon is seen trying to eat his own entrails before he dies. They only let themselves be enslaved by Yeerks in exchange for a continuous supply of food, and the slim hope that having an overriding parasite could help overwhelm their racial hunger. NOPE!
Ambiguously Gay: Gafinilan and Mertil. They either have a very close and important friendship or the most well-written romance in the whole series. We don't get definitive evidence either way.
Amicably Divorced: Variations: Rachel's parents, Dan and Naomi, are uncomfortable spending time together, but they'll do it. On the other hand, she's friendly enough with Jake's parents (her ex-husband's brother and his wife) that she'll dog-sit for them when Jake's mom's grandfather passes away, while she and Jake still refer to each other as "aunt" and "nephew." And on the other hand, she and Saddler's parents don't really get along, but her family still "helps out" once he's in the local hospital.
Ancient Astronauts: The Pemalites (multiple books) and the Nesk and Mercora from Megamorphs#2
And Then What?: The characters often try to convince themselves, and each other, that after they've saved humanity from a race of alien parasitic monsters, they'll just go back to being regular kids. Yeah, right.
And I Must Scream: If you're infested by a Yeerk, then your memory and body is completely at his command... And it leaves your mind and intelligence intact, completely unable to do anything other than watch your "guest" do all sorts of horrible things. The Yeerks themselves suffer this in their natural state, being blind, mostly deaf slugs who just happen to be sentient.
And the Adventure Continues: The series ends after a couple of timeskips with Marco, Jake and Tobias heading into a battle while in search of Ax.
Animal Motifs: Each of the Animorphs has a few favorite morphs that they use consistently, particularly in battle, that tends to say something about their personality and fighting style. For instance:
Rachel's favorite battle morphs are grizzly bear and elephant, neither of which is particularly subtle or defensive.
Jake's favorite battle morph is a tiger, which is known for its intimidating appearance.
Cassie purposely chooses a wolf morph for combat, even after she acquires far more powerful animals, as she hates fighting and prefers not to seriously hurt her opponents.
Later in the series her Hork-Bajir morph become her default battle morph; morphing a sentient being despite her convictions that it is wrong to do so represents the conflict between her role in the war and her pacifist nature.
And obviously, Tobias is the hawk. Even after he regains his morphing ability, he often goes into battle in his now-default hawk form.
Ax also often goes into battle unmorphed, since Andalites are plenty dangerous in their natural state (extremely sharp tail blades, remember?)
Finally, Visser Three has a grab bag assortment of alien morphs, but the only one he uses more than once is the 'Eight', the bizarre eight-headed, eight-armed, eight-legged, fire-breathingabomination he uses in the climax of the first book. Besides setting up the Visser as an alien threat of monstrous proportions, this particular morph owes a lot to the Beast of Revelations.
Anti-Hero: All the Animorphs are this as they do some rather unsavory things while fighting the yeerks.
Ant War: Done intentionally to get ants off an unconscious Rachel.
Anyone Can Die: Death of named characters is incredibly rare before the final arc begins, particularly if the character has appeared in more than one book, but quite a few of the supporting characters (Jara Hamee, Tom, Edriss, Arbron, James, and the Auxiliary Animorphs) and two of the main characters (Rachel and Ax) are dead by the series' end. Possibly more; the only main character confirmed to be alive after the Bolivian Army Ending is Cassie.
Apocalypse Cult: Two years after the Yeerk defeat Jake finds work training a morph-capable counter-terrorism unit created in response to a spate of attacks on alien tourists. Apparently some of the worst are perpetrated by cults that think the presence of aliens on Earth is staving off a long-awaited apocalypse.
Archaic Weapon for an Advanced Age: Ax notes at one point that human firearms are no match for the energy weapons of the Yeerk and Andalites, but still do a good job of blowing large, messy holes in you.
Arch-Enemy: Visser Three to the group collectively, although especially to Ax. And to Elfangor, before he died. Then there's Crayak to the Ellimist, Taylor to Tobias, and David to Rachel.
Arson, Murder, and Jaywalking: In Visser the charges against the former Visser One are read during her trial, followed by the different forms of death penalty associated with each crime. It ends almost incongruously with "... treason by murder of subordinate Yeerks, which carries a sentence of exile to punishment duty."
Ascended Fanboy: The Ellimist, arguably. He starts out as a gamer on his homeworld and eventually turns into a near-omnipotent being playing "games" with Crayak. Also the campers from The Resistance, who are Star Trek fans on their yearly camp out to look for aliens or something. Not to mention Erek.
Asskicking Equals Authority: Visser Three, in The Andalite Chronicles, is a Hork-Bajir Controller with the respectable rank of Sub-Visser Seven. He's promoted to a low Visser rank immediately upon (and explicitly because of) his infestation of Elfangor's commanding officer and becomes the only Andalite-Controller in history. His rise turns meteoric from there.
I wondered about the image of Hork-Bajir and humans living side by side if the Yeerks were defeated. Humans didn't have a great record of getting along with people different from themselves. Humans killed one another over skin color or eye shape or because they prayed differently to the same god. Hard to imagine humans welcoming seven-foot-tall goblins into the local Boy Scout troop when they couldn't even manage to tolerate some gay kid.
A major motif in this series is the fact that there are some things that you just can't unlearn. The kids can't, although they desperately want to, forget about the Yeerks and go on living their lives, because they now know they'd be dooming the entire planet to enslavement; to quote a Megamorphs back cover, "You can't close your eyes to the truth you know is out there".
Bad Boss: Visser Three (promoted to Visser One during the series). Not only does he sarcastically mock his subordinates, but he kills them for little-to-no reason. Didn't kill the Animorphs? Decapitated. Made a mistake? Decapitated. Interrupted the Visser? Decapitated. Closed a door too slowly? De-fucking-capitated. You can't win with this guy, to the point where Yeerks pass over promotions because it means having to work with Visser Three, and therefore probably being decapi-SLASH- *thud*. Lampshaded: Jake points out that Visser Three's tendencies to kill his subordinates make them hate and fear him, making him (and them) less effective. He also says that that gives the Animorphs an advantage over him.
Both the Blade ship and the Pool ship qualify (the former is a battleship, the latter is more of a barracks and Airborne Aircraft Carrier with big fucking guns).
On the Andalite side, we have the Dome ship, with the titular domed reproduction of the Andalite homeworld that detaches for greater maneuverability in combat.
Balance Between Good and Evil: The Ellimist and Crayak tie each other's hands as to what they can or cannot do. If one wants something, they have to make a concession. Both do plan on eventually defeating the other forever, however.
Bears Are Bad News: Rachel, always on the edge between Action Girl and Blood Knight, loves her grizzly morph. The characters consider their polar bear morphs to be their most dangerous, with good reason. Rachel was killed by a Yeerk in polar bear morph.
Rachel, as a human, according to everyone else. But her morphed battles have included chewing through her own tail and whacking Mooks with her own severed arm.
Averted in #41: When a grown-up Jake encounters the future version of Rachel, she is severely crippled: One of her arms has been cut off, both her legs are missing, she's missing an eye and her face is grotesquely scarred.
Be Careful What You Wish For: In the first book, Tobias states he's alright with his red-tailed hawk morph and doesn't want to be anything else. Consequently, the end of that episode (and the whole rest of the series) sees him trapped in that shape.
Belligerent Sexual Tension: It's hinted that Rachel and Marco's playful rivalry in the early books might be this, particularly on Marco's part. It begins to take on much darker and nastier undertones as the war wears on.
Human-Controllers (Yeerk hosts) generally have public personae falling between "normal but caring human" (Chapman) and "Friend to All Living Things" (William Roger Tennant). The Sharing, "a Boys & Girls Club for everyone" responsible for a great deal of youth work and charity events, is a Yeerk front organization intended to recruit new Controllers.
Cassie, who is dangerous exactly because she's nice. Remember, she felt it would be kinder to trap David in rat morph on a tiny rock-island in the middle of the ocean instead of just killing him. She also lets Tom escape with the morphing cube, because Jake, his own brother, would have had to kill him to get it back, which caused Ax to wonder if Cassie could be more dangerous than Rachel.
She also chose to erase Visser Four's host body from existence, prompting the Drode to mock her for "killing them with kindness".
Big Bad: Visser Three takes this role for most of the books, as the leader of Yeerk forces on Earth.
Bigger Bad: Visser Three's the main villain of the series, but he does have mostly off-page superiors, namely the Council of Thirteen and Visser One (the original, before he takes her position), and then there's Crayak...
Tom does everything he can, which isn't much, to keep his brother from being infested and goes nuts at the thought of the Yeerks getting to Jake. Jake displays a similar protectiveness towards Tom besides being younger. Also, Elfangor towards Ax.
At one point in the series, when Jake and Controller Tom are talking (which they do often, being brothers, obviously), "Tom" lies to Jake to cover his status as a Controller, and, if only for a second, Jake notices Tom's face twitch strangely. Jake suspects that Tom is trying so hard to fight against his Yeerk that he momentarily wrestled control of his body away from the Yeerk, which is pretty much established as impossible.
Biological Weapons Solve Everything: The Andalites tried to do this to prevent the Yeerks from enslaving the Hork-Bajir race (by way of a virus that only affected the Hork-Bajir), but eventually failed.
Bittersweet Ending: While the war is over and things are looking up for humankind, Rachel and Tom are dead, Tobias has fled to the woods, Jake's guilt continually drives him deeper into depression, Cassie has had to leave Jake and the Animorphs behind in order to move on, and even Marco's happy rock-star life is bittersweetly shallow. Ax seems comparatively well-off to begin with, being promoted directly to Prince in the Andalite military and later given his own ship to command, but his capture and apparent assimilation by the new Big Bad is what leads to Jake, Marco and Tobias flying off into space and running headlong into the Bolivian Army Ending.
Black and Gray Morality: A major theme in the books. Definitely applicable by the end of the series. Can also cover the Andalite military, who are just as bad as the Yeerks, just in a different way.
The Taxxon's insatiable hunger certainly fits. The Yeerks' parasitism, which is all fine and good until one becomes conscious of one's status as a parasite. The morphing power itself may qualify, as once the kids gain it, they can't really enjoy it as they're caught up in an interplanetary war.
Andalites and their thought speak. It's cool being partially psychic, but the lack of mouths meant it took the Andalites centuries to develop alternatives to things like telephones.
The whole Animorphs gang, really. And at least Tobias was stuck as a hawk, not a flea. Or a rat.
The Yeerks make the Hork-Bajir Cursed with Awesome as well. They're used as shock troops for combat because they're strong, agile, and just about every moving part on their body has a wickedly sharp blade sticking out of it. The thing is, those blades? Uninfested Hork-Bajir use them to harvest tree bark, their main food source. The whiplash musculature and quick movement come from the fact that they're an arboreal species that prefers to avoid predators entirely, rather than fight off attackers.
Blood Knight: Rachel tries not to fall into this. More often than not, she fails horribly. During The Separation, when she gets split into two different personalities, one of them is a Blood Knight personified, interested ONLY in fighting. She's still somewhat interested in Tobias while like this, but that interest takes a secondary seat to violence.
"It was a scene of perfect beauty. Blood slicked the concrete. Taxxon guts lay in steaming piles. There were bellows and cries of pain. Battle! Desperate and deadly! I almost cried at the sheer loveliness of it."
— The Separation.
Bluff the Eavesdropper: Once the team realizes how unstable and dangerous David is, they sometimes do this while discussing their plans, in case he is eavesdropping on them in morph.
Body Horror: Most of the morphing is this, except for Cassie, who has a talent for it. If a morpher hits the two-hour mark mid-morph, they get Mode Locked as misshapen monsters stuck between their morph and their real form.
The kids remark from time to time that they only thing they find strange anymore is that they don't find anything strange anymore. Constantly lampshaded by Marco, who often remarks, deadpan, on how utterly insane their lives have become.
Let's see: started with aliens, added shapechanging, destroyed some spaceships, traveled through time...again, manipulated by god-alien, bartered hair and holograms for tour guide on distant planet, the oatmeal issue...and that's just the beginning.
Break The Game Breaker: The Animorphs get the chance to acquire dinosaur morphs when they go back in time; the ending provides a Snapback so that they cannot use these morphs in the future; random Techno Babble at the end of the book gives us an explanation why.
Book 51 (The Absolute) is a pretty good example. The two episodes right before it and the three right after it were some of the darkest books in the series, filled with emotional trauma and huge changes to the status quo. Book 51, on the other hand, is basically one big chase scene, and although it does change the status quo some when the Yeerk invasion is made known to the public, it doesn't end up mattering too much.
Another good example is Book 20 (The Discovery). It came right before two of the darkest books so far and right after The Departure, a Wham Episode. However, the book itself is pretty light and primarily funny rather than dramatic.
Book 32 (The Separation) stands out for being relatively light, compared to the thee books before it (many of which were on the borderline of Wham Novels) and especially to the one after it. Also, other than introducing the AMI, it didn't introduce much to the continuity.
The Bridge: The Pool ship's bridge and the Blade ship's bridge are the locations of some very important events.
The Brute: During the last story arc and the books leading up to it, the kids reflect that Visser Three is an incompetent tactician and instead relies on technological advantages; he's pushed for all-out war since the beginning. "[He] doesn't know tactics," Jake says, "he fights with a sledgehammer."
Brother Chuck: Hey, remember Mertil, the Andalite that had also survived Elfangor's ship's crash and had been living on Earth for the entire war? Remember how he was found by the kids and decided to remain in hiding? Or maybe you don't, because he was only in one book. Having another Andalite on board would've been very useful for the kids. Even if Mertil didn't join the kids for his own reasons, it would've been nice for him to get another mention, seeing as an Andalite war hero living on Earth is kind of a big deal.
Broken Masquerade: James and his friends, the Carpenters, and the Animorphs' parents. The kids' parents have a very difficult time adjusting, except for Eva, who adjusted a long time ago. This escalates to the entire world when open war is declared, especially in the last book of the series.
"It's all your fault! I used to see you as a hero, Elfangor. A leader. But the truth is you just couldn't see another way out! You sentenced us to hardship and pain and suffering. We were just kids! You made us question every value we had ever learned! You had no right to heap that weight on us, huge and impossible. You used us!"
Andalites in general for all of the kids. At the end of the series they found out the Andalites were planning to take advantage of the Animorphs' complicating the Yeerk conquest and forcing them to concentrate more and more forces on Earth. Unfortunately they were going to do it by glassing the planet to kill as many Yeerks as possible in one fell swoop. Then flipped around: it turns out the Andalite civilian population is wholly against this, and public opinion forces the Andalite naval commanders to back down and accept the Animorphs' solution of turning any Yeerks willing to surrender into animals.
Breather Novel: Book #24, The Suspicion. Tiny aliens invade Cassie's barn and try to steal the morph cube. Hilarity Ensues. Made all the more blatant as a breather because it comes right on the heels of a major Wham Novel.
Bullet Time: A trick frequently used by K. A. Applegate; when one of the characters are on the edge of death, in battle, time seems to slow down. It's never explicitly called bullet time, though.
Bug War: The war on the Taxxon planet in The Andalite Chronicles.
Busy Beaver:When Jake morphs into a beaver his mind fills with thoughts of "Work! Work! Work! There is work to be done!"
But Not Too Black: Inverted in the relaunch of the series, with fans complaining because the model chosen for Marco wasn't Latino enough.
Bystander Syndrome: Initially, the kids see the Yeerk war as strictly between the Andalites and the Yeerks, which is why Marco is so against getting involved. However, when Jake learns Tom is a Controller, the kids realize that the stakes are much closer to home than previously thought. By the end of the series, the kids have lost their faith in the erstwhile Andalite reinforcements, and have concluded that it's all up to them.
Cain and Abel: Tom and Jake, respectively, though in an interesting subversion, in this case it's the Abel that kills the Cain. That particular subversion appears to be a favorite of K.A's. She also uses it in Everworld.
Can Only Move the Eyes: Sometimes Controllers can break through the Yeerk's control to portray a meaningful glance or facial expression.
Used in an attempted Taking You with Me in Visser when Visser One's host gains enough control of her eyes to blink in heavy traffic.
Can't Stay Normal: Cassie is a sub-temporally grounded anomaly. When the Drode reworks reality so that the kids never got the morphing power, allowing them to stay normal kids, Cassie's mere existence causes the new reality to go haywire, with people randomly teleporting between locations and coming back from the dead. Depending on how you look at it, Cassie either can't stay normal, because having animal morphing powers from alien technology is the the true reality and any attempt to deviate from that will end up breaking reality, or she can't stay abnormal, if you postulate that "animal morphing powers from alien technology" is her normal.
Nobody believes the kids the first time they explain what's going on.
At one point the Andalites are sending the majority of their reinforcements to the Anati system instead of Earth, believing the majority of the Yeerk fleet to be there. The kids have inside information that the Anati system situation is an ambush (the asteroid fields are rigged with automated turrets and mines). When they hear this, the Andalite command assumes the kids are lying in an effort to become a priority.
Jake's "Don't call me Prince." is something between this and a Running Gag.
The Cavalry: During the fourth book, the Animorphs in dolphin morph save a whale from sharks. Later, they are being chased by the Visser in the morph of an alien sea monster. The whale family shows up and saves them. The exact same thing happens in book 36, oddly enough, also involving whales.
The whole series is really about walking the line between this and Break the Cutie. The humans characters start off the series as five more or less normal kids. By the end, three years later, they are, respectively: a ruthless leader willing to sacrifice anyone at all to win, a bloodthirsty killer who honestly believes that she could not survive in peacetime, a boy who willingly severs all ties with humanity and never looks back, a strategist so obsessed with the "bright, clear line" between himself and victory that he can't turn away from it, and a vicious manipulator who has given up on just about all of her principles. Whether this is character development or character damage is anyone's guess.
Comes Great Responsibility: Tobias is very serious about this in #1. Jake also notes in MM3 that their power traps them in a bind: they have enough power to fight and make them responsible, but they don't have enough power to actually win.
Comic Book Time: Played with. Early books in the series had the Unreliable Narrators worry about how they would adapt in winter, which implies that their adventures are taking place in Comic Book Time prior to the first winter after receiving their powers. By the end of the series it turns out that It's Always Spring because of the setting, the worries about winter playing up the Literary Agent Hypothesis that they could not give away their location, and about three years pass from beginning to end of the series.
Commander Contrarian: Marco, for two reasons. Firstly, because the kids' plans are usually slapped together at the last second or played by ear and therefore incredibly risky ("This is an insane plan!"); secondly, because Marco has a talent for zeroing in on inconsistencies, and wants to make the plans as effective and watertight as possible. It's said that pointing out flaws is really all Marco can do, which is what makes him a bad leader, as he's too cautious to actually get anything done. It also makes him the best tactician of the team, as is often pointed out. He couldn't make you go along with it, but he could hammer out a working plan well enough.
Common Tongue: Gallard is a galactic language designed to be pronounceable by pretty much anyone. It doesn't see much use (although Hork-Bajir occasionally lapse into it) because the primary aliens are the telepathic Andalites and the Puppeteer Parasites Yeerks.
Contest Winner Cameo: Erek King. Actually became a recurring character, and a major player in the final battle.
In the very first book, it's possible for a human to thought-speak with someone in morph, which is totally ignored in every single other book.
Due to the fairly large number of these in the series, the fandom nicknamed them KASUs or "Katherine Applegate Screws Ups/Screw-Ups" (K.A. herself eventually started using the term in interviews) and when the first few books were relaunched in 2011, they were fixed.
A whole list of KASUs can be found at this page: "A List of Mistakes in Animorphs"note Archive generated by the Internet Archive's Wayback Machine (dating back to October 27, 2009), due to the closure of Yahoo GeoCities..
In #54, Ax was promoted from "aristh" straight to "Prince," calling back a conversation between Elfangor and Arbron in The Andalite Chronicles, where Arbron snarks that glory-hungry Elfangor's probably fantasizing that they'll make him a Prince without even stopping to make him a full warrior.
In the last book, when the Rachel is about to battle the Blade ship. The Rachel's weapons can't penetrate the Blade ship's shields, so Jake orders to "Ram the Blade ship". Almost twenty years earlier, Elfangor had issued the exact same command, which won the battle and earned him the rank of War-Prince.
"We're not morphing ants! We're never morphing ants again!" or some variant is said every couple books, in reference to one of the kids' earliest missions.
When Marco morphs lobster to get his keys from the bottom of his pool: "It seemed like a lifetime ago that me and Jake morphed lobsters to escape from the Yeerks by hiding in a grocery store fish tank. The days, man. Those were the days."
In the penultimate book, Jake flushes thousands of unhosted Yeerks out of the Pool ship into space. This is exactly what Elfangor refused to do back in The Andalite Chronicles, showing that Jake is now far more ruthless than Elfangor was (at least at first).
Conspicuous CG: You think a book series would be immune to this? Every book features artwork by David B. Mattingly, except the covers done by Romas Kukalis. Most of the first-page illustrations were created by David as either photo manipulations or photo montages. Two, however, stand out. The illustrations for Book 31◊ and (to a lesser extent) book 38◊ use more CG than normal.
The Animorphs contain Ax (Elfangor's brother), Tobias Elfangor's son, Marco the son of Visser One's host, and Cassie a sub-temporally grounded anomaly, meaning that her involvement/existence will eventually break down any attempt to rework reality. The Drode lampshades this, insisting it can't be a coincidence, and that the Ellimist stacked the deck.
There are several apparent ones in Book #27, but it is ultimately an aversion. Erik is left unable to move or project his hologram, so the Animorphs carry him out of the mall. There was a major sale, so virtually everyone was elsewhere in the mall and all the cameras are down. They take a bus, and the bus driver doesn't notice. This makes them suspicious. Later, when they realize they will need a sperm whale morph, a sperm whale "happens" to beach itself. This they all realize can't be a coincidence, and that someone is pulling the strings. The Drode turns out to have been behind all of it.
Cool Starship: The kids themselves are partial to Dome ships, especially newer models like the Elfangor. The Rachel is also supposed to be pretty sweet.
Cosmopolitan Council: The Yeerk Empire is made up of officers called vissers, who take orders from the Council of Thirteen.
Covered in Mud: At one point, Cassie jokes about how Rachel never seems to get dirty - that any mud just seems to be deflected away. She throws a ball of mud at Rachel, who knocks it away without it splattering all over her. Cassie comments that Rachel's hand probably isn't even muddy, but Rachel refuses to show her.
Covers Always Lie: The cover for Visser features a picture of a mature Andalite with a sinister expression. The logical assumption is that this book is all about Visser Three. Turns out it's all about Visser One, and Visser Three is a supporting character.
Creator Provincialism: It's not really made clear what's going on outside the States during the entirety of the war. We know that at least one major head of state outside the U.S. is a Controller (the President of the U.S. isn't though), but except for, like, four missions outside the country, the kids mostly ignore everything beyond U.S. borders. Or more than a day's journey from their home town, for that matter.
The Cretaceous Is Always Doomed: In Megamorphs 2: In the Time of the Dinosaurs, a hole in space-time causes the Animorphs to accidentally arrive one day before the asteroid hit. They get into a tussle with several warring Ancient Astronauts trying to colonize Earth, the losing species attempting revenge by diverting the path of a passing comet. The meteor's strike creates another hole that lets the kids return to the present. It was one of the weirder books.
Tobias: <No one wants to ask you because they think maybe it's rude. But everyone wants to know how you eat with no mouth.>
Ax: <How do I eat? Well, I have hooves, don't I?>
(It's later revealed that Andalites absorb nutrients from grass through their hooves.)
Curb-Stomp Battle: Erek King, the millennia-old robot that is capable of generating personal forcefields and shrugging off being hit by a truck. He can move faster than the eye can follow and is described as being able to "obliterate you down to your individual molecules"; however, he's hardwired to hate violence and can never commit any violent act. In one instance, this is subverted, allowing him to rescue the Animorphs. The fight lasted less than a minute, and was only vaguely described. In the time it took you to read this paragraph Erek managed to kill dozens of Hork-Bajir. Afterwards, Erek begged to have his original protocols restored. Rachel saw it and the brutality reduced her to tears.
Dark and Troubled Past: Marco. The disappearance of his mother and the subsequent split of his family caused him to become more cynical and, in effect, more ruthless and pragmatic and less attached to romantic, idealistic principles.
Dark Is Evil: All of the yeerk ships are described as a very dark black color
Deadly Decadent Court: While the average yeerk is not necessarily Always Chaotic Evil, their government is an absolute circus of depravity and murder. The various Vissers are constantly trying to kill their higher-ups, while their underlings jockey for power underneath them and occasionally try to take their jobs in the same way. Meanwhile, the Council of Thirteen, who runs the Empire, works with the identity of which one of them is the Emperor concealed from the others, since they all fear his assassination. At one point, when the Animorphs launch a raid on the trial of Visser One in VISSER, the Council, safely present only in holographic form, enjoys the spectacle like sports fans, taking bets on the outcome, cheering and booing one side or the other, all that jazz. One, in a taxxon host, is so overcome with emotion that he grabs a passing clerk and begins eating him alive.
Kid Hero: It's obvious from the get-go that the kids, having no sort of military knowledge or practical connections whatsoever, are pretty much just making it up as they go and doing the best they can with what they have, and they're closer to Child Soldiers than anything else.
Wake Up, Go to School, Save the World: As you'd expect, fighting as an uncover guerrilla resistance agent tends to take up a lot of the kids' spare time and energy, and is too important to leave to an extra-curricular schedule. The war takes place at the expense of the kids' personal lives (sometimes forcing them to fight for up to, it is mentioned, three days straight without sleep) and their grades and sociability are pretty much done for by the end of the series.
The Good Guys Always Win: Played with. The kids actually do manage to save their home planet, but the fact that they're massively outgunned is a major element in the story, and the kids comment from time to time that only rarely are their missions actually successful. One of the major messages of the series is that, despite idealistic platitudes, victory ultimately goes to those who are ruthless and desperate enough to take the most extreme measures, not to the morally superior.
Throughout the whole series, Jake and the kids wait for Andalite reinforcements to save them from the Yeerk invasion; originally, Elfangor had promised them that they would have to fight for no more than a year. This year eventually stretches into three, as Andalites see humans as a low priority and take their time getting there. Unfortunately, by the time the Andalites arrive, they've realized they've made a huge mistake: the Yeerk presence on Earth is much larger than anticipated (in the rare instances where the kids made contact with Andalites, the Andalites assumed they were lying to become a top priority). By that time, the secret war has erupted into a full-blown conflict, so the Andalites decide to wait for the Yeerks to completely commit their forces planetside. Once that happens, they will "quarantine" Earth: A nice way of saying that they're going to completely sterilize Earth from orbit to kill everything, Yeerk military and humans alike.
When the Yeerks invade the Hork-Bajir planet, the Andalites send only minimal reinforcements. When it's made clear that the Yeerks are winning, Alloran creates a quantum virus that will kill every Hork-Bajir on the planet, in order to make sure that a minimum number of Hork-Bajir can be used as hosts.
Eventually averted in the last book. Prior to the last book, Ax notes that the prolonged war against the Yeerks has given the Andalite military command more power than they rightly should have, and they no longer properly represent the will of the people as they're supposed to. This comes to be proven true in the last book, when Ax invokes his legal right to challenge the decision of Andalite Captain-Prince Asculan regarding Jake's promise to Yeerk prisoners on Earth, by which Ax's challenge would be tried before a civil court as opposed to a military one. It is heavily implied that the civil government and the people are surprisingly supportive of the human victory; Prince Asculan is forced to consult with his political advisors, and, realizing that he doesn't stand much of a chance in a civil trial, Asculan begrudgingly bows to Jake's wishes.
Marco gets brought back to life twice. Although in one instance, he's not technically dead, just comatose, because he's in cockroach morph, which is practically unkillable.
In Elfangor's Secret it's known that one of the kids will have to die to set things right, and Jake is shot in the head as they cross the Delaware. But because Visser Four's host is retgoned, there was no reason for them to travel through time in the first place and Jake pops back, alive. In addition, because Jake is dead and the Ellimist said only one Animorph would have to die, the rest of the Animorphs are invincible for the rest of the book, even when they should by all means be dead.
Deus Angst Machina: Pick a character, any character. Especially the auxiliary Animorphs. And, in a weird way, Loren.
Deus ex Machina: To the Leeran conflict, the Animorphs could be considered this. They are not supposed to be there, show up right when all hope seems lost, and happen to have the exact abilities needed to ensure Andalite victory there.
Devil's Advocate: Marco would sometimes offer the Devil's Advocate view on missions.
Did Not Die That Way: Marco believed that his had mom died in a boating accident, but it was a cover so the Yeerks could get her away without a lot of questions.
Diminishing Villain Threat: Visser Three. He's completely immoral and monstrous, but as a consequence of appearing in almost every book and not killing the Animorphs, he quickly starts to come across as a blundering clod. Visser One even acknowledges this in the Visser Chronicles, comparing him less-than-favorably to the Helmacrons. While he does get promoted to Visser One towards the end, he still doesn't undo a lot of this.
It becomes funny when even Visser Three starts noticing the effect. "Would it be too much to ask for one of you to actually HIT SOMETHING?!?!"
Disability Superpower: Literally. Most of the Auxiliaries are hospitalized children, as Yeerks are less likely to infest the disabled. It's mentioned that they have a much easier time controlling the instincts of a new morph, as their minds are stronger from spending so much of their lives unable to move their bodies as freely.
Does Not Like Shoes: As morphing results in lost or destroyed shoes, the Animorphs are frequently barefoot. Every book mentions this fact and sometimes describes what the characters are feeling underneath their feet as they go about their adventures.
This is frequently deconstructed, when their lack of shoes causes problems, but played straight in the Andalite Chronicles, when Loren takes off her shoes and socks in the Dome ship, even though the Andalites though she was ripping her "hooves" off, much to their horror.
The Dog Bites Back: Tom's Yeerk. Guess Visser Three should have promoted him when he had the chance.
Don't You Dare Pity Me!: Marco hates being pitied by the others, and often shoos Cassie away when she tries to play therapist. Jake, similarly, can't stand pity, because he feels that as the leader, he should appear flawless and confident in every decision he makes, and therefore tries never to let the others see him second-guessing himself.
Doomed Hometown: Bug fighters destroy the kids' hometown in the second last book to create a giant dead zone around the Pool ship's landing site. They reduce the entire city to a desert of ash, so the nothing can get close without being seen.
Door Stopper: Not the books themselves, but Marco mentions picking Lord of the Rings for a book report. Three books long, and each as long as three books.
The Morphing technology grants you your animal form's instincts as well as your own consciousness. Sometimes these play well together, sometimes not. It usually depends on how humanlike said animal is. Tobias struggled with this while in Shapeshifter Mode Lock in some early books, then came to terms with it.
The kids wonder about the morality of morphing, as controlling the animal's natural mind is similar to what Yeerks do to humans and the kids decide early on to never morph sapient species without the permission of the person. Near the end of the series, some missions become impossible to accomplish without morphing human or Hork-Bajir, so the kids compromise their morals. By the end of the series morphing Hork-Bajir is commonplace and Tobias uses it as a battle morph.
In Visser, Visser One is freaked out by the Humans Are Special feature of a two hemisphere brain, and can't understand how a creature that is always arguing with itself could possibly function.
The Drag-Along: Marco initially, though he eventually grows out of it.
Drama-Preserving Handicap: Initially, it's in both sides' best interest to keep the war a secret. The Yeerks prefer a strategy of infiltration, then suddenly seizing control of the planet, in order to minimize both Yeerk casualties and the deaths of thousands of potential host bodies. The Animorphs, on the other hand, prefer the war also remain a secret, for tactical reasons: the Yeerks have much more advanced technology and would certainly win any open engagement where they were free to use all of their weapons (a bunch of animals can't do much good against Yeerk capital ships destroying cities from orbit). Also, the primary reason the Yeerks want Earth is because of the large population, and a war would reduce the value. On the other hand, there are so many damn humans compared to Yeerks (6 billion versus a couple hundred thousand) that open warfare might even hurt the Yeerks despite their serious technology because humanity could and probably would Zerg Rush any terrestrial fortifications, at least enough to turn the campaign into a Pyrrhic Victory that the Andalites could take advantage of.
Drawing Straws: Used routinely to decide who is put on a mission when the Animorphs are making it up as they go (which is often).
Ax: < The human scientific method. >
Dream Sue: When Jake becomes a Controller early on, one way the Yeerk tortures him is by replaying an embarrassing fantasy of Jake's from years prior, where he won the big basketball game with a difficult shot and was then congratulated by Tom (a much better basketball player).
Dreaming The Truth: It turns out #41 was all a mind exercise, during which Jake rediscovers the things they're fighting for in the first place.
Dumb Is Good: the Hork-Bajir in there normal state are rather dumb by human standards but still nice.
The Dung Ages: Invoked in Elfangor's Secret, which emphasises just how awful personal hygiene was in medieval times. Everyone at Agincourt, including the King of England, is covered with sores, missing teeth and crawling with lice. Ax quips that if the Yeerks had arrived in this era, they'd have decided humans couldn't support any more parasites. The time-travelling Visser sticks out largely because he doesn't have a face full of holes.
Dying as Yourself: A host will sometimes experience a moment of freedom before death as the Yeerk will abandon them in an attempt to save themselves.
Early Installment Weirdness: The first ten books have a disproportionately large number of KASUs and introduce a lot of plot points that are never mentioned again, including book one has Elfangor being able to put in the kids' minds an image of what a Yeerk looks like, while later books include no evidence ever again Andalites can send people images psychically, and Hork-Bajir having a biological imperative to make war with each other every sixty or so years (later books indicate Hork-Bajir don't even live that long) and the warning that Yeerks have infiltrated the Andalite home world, which never goes anywhere.
After years of unimaginable pressure and War Is Hell torment, the kids become the greatest heroes in the history of humanity. However, only Marco, Cassie and Ax get to profit from it - Jake's clinically depressed due to his actions aboard the Pool ship, and Tobias struggles to live a solitary existence in the woods.
And Rachel, who died in the final battle.
And, of course, thanks to the budding Kelbrid war and Ax's kidnapping, life turns out pretty shittily for everyone.
Well, except Cassie.
Earth Is the Center of the Universe: While initially it seems that Earth is simply the next planet on the Yeerk list to conquer, it soon becomes apparent that it attracts more attention than the rest; the Humans Are Special factor is what attracts the Yeerks themselves, while the Skrit Na have already been here before the other present-day races. Then there's the fact that the Mercora decided to settle down on it at the end of the Cretaceous, resulting in a fight with the native sentient ant species, and to cap it all off, before any of that happened, the Ellimist recalls a fight wherein Crayak took potshots at the planet with some giant weapon and he had to bat them away like a galactic baseball game. In short, Earth is the one planet every race in the galaxy has come to.
Electric Instant Gratification: Worked into an Electric Torture device, and proves more effective on hawks than standard torture. A hawk can handle torture just fine; animals are good with dealing with pain. But a hawk doesn't know what to do with that kind of pleasure, and lowers its defenses for when the torture comes back.
Perhaps the most important one is the above-mentioned rivalry between Vissers Three and One. Visser One is just as bent on world domination as Visser Three is, but she and the Animorphs agree that things would be worse for all of them if Visser Three overthrew her, at least for the time being.
In Book 24, the Animorphs attempt to convince the Helmacrons to take out Visser Three for them, but the Helmacrons turn out to be so annoying they agree to a temporary truce with Visser Three just to get rid of them.
In Elfangor's Secret, the Ellimist and Crayak both agree that the Time Matrix should not be in the hands of a mere mortal and help the Animorphs stop Visser Four.
In the last few books, they team up with Tom and his followers in order to hijack the Pool Ship. Both sides then double-cross each other, but the Animorphs end up winning in the end.
Engineered Public Confession: Or rather, an engineered public demonstration. In Book #35, after spending days harassing a particular famous-but-psychologically unstable Controller, Marco (as a poodle) provokes the Controller into attempting to strangle him to death on national TV.
E.T. Gave Us Wi-Fi: In The Andalite Chronicles it's implied that Elfangor made friends with Bill Gates and Steve Jobs, which led to the advancement of human technology. Also played with in #45 The Revelation, when it's revealed that the Yeerks helped humans discover Zero-space. Lampshaded by Ax in the same book.
Even Evil Has Standards: A good deal of the series' ambiguity revolves around the differing customs and ethical values of humans, Andalites and Yeerks which make it very difficult to draw the line between moral and immoral warfare.
Jake: He's a prisoner of war. We don't kill prisoners. Visser One: No. Of course not. You merely blow up ground-based Yeerk pools and kill thousands. And then another seventeen thousand of our brothers here on this ship. Defenseless, harmless, unhosted Yeerks. Murdered. But you don't kill prisoners.
Visser One (not Eva, the actual Yeerk) and her human children, who were, oddly enough, allowed to remain uninfested during their time with her.
David's main motivation is to free his parents from Yeerk control, but since he doesn't know about starving out Yeerks, he tries to make a deal with them instead. Once that's off the table, he tailspins real fast.
In The Alien, a minor Yeerk agrees to help Ax assassinate Visser Three in revenge for the Visser allowing his lover to die of Kandrona starvation.
Everyone Can See It: Despite initial trying to keep their relationship low-key, it was very apparent to everyone that Jake and Cassie were smitten with each other. Marco also sarcastically makes the same observation in an early novel when Rachel pulled a He Is Not My Boyfriend regarding Tobias.
The Ellimist. Oddly, Ellimist was originally his online gaming handle, which he adopted as his name when he ascended to omnipotence. His real name is Toomin.
And the Drode. According to the... er, being himself, it means "wild card."
Everyone Meets Everyone: Partially subverted. Each of the five main characters knew, or at least knew of, the other four before the series began, but they weren't close.
Everyone Loves Blondes: Rachel appears to be just a pretty face as she is tall, graceful, blond haired, blue eyed, and glamorous but her fearlessness makes her more than that.
Evil Gloating: A couple times in minor books, but most notably done by Tom's Yeerk in the final two books (narrated from different perspectives):
"You appear to be experiencing some engine trouble, Visser," Tom said, gloating. <The Empire will track you down and kill you for this, you do understand that, I hope?> Visser One said. "Oh, I doubt it," Tom said cheerfully. "The Andalite fleet is rather close by. It's possible that I misled you on that point." He was all but giggling.
Evil Overlord: Visser Three. The first Visser One might also qualify, as things she does are undeniably ruthlessly evil, but they're more motivated by her military goals than an inherently malicious personality.
Eviler than Thou: The whole hierarchy of the Yeerk Empire, but particularly the Visser One/Visser Three rivalry.
Evil Me Scares Me: Rachel gets this several times- when she gets split in half; when she gets turned into a monster; when she gazes into the abyss of her soul and sees a fearsome Blood Knight staring back at her.
Exposed Extraterrestrials: Pretty much all the aliens, particularly the Andalites, who first thought that human clothing was part of human's bodies. Ax has trouble understanding why he has to wear clothing while morphed as a human.
Faking the Dead: More than once. Visser One sets it up so that it looks like Eva, Marco's mother, drowned at sea, so that she had an excuse for disappearing into space. Later, Marco has Erek and Mr. King stand in for himself and his father when the Yeerks come to kill them. Finally, Jake fakes the deaths of all the other Animorphs in order to sneak them on the Pool ship in his final Batman Gambit.
Family-Unfriendly Violence / Family-Unfriendly Death: The fight scenes in this series are quite graphic. Ripping out throats, hacking off limbs, stabbing, shooting, maiming, disemboweling - you name it, someone's done it. What makes the violence notable is that because morphing heals every wound the Animorphs have, the same character can have the same limb hacked off multiple times.
"JAKE, STOP HER!" Tom, right before Rachel kills him.
"I love you." Rachel, to Tobias.
"Do the right thing." David, to Rachel.
Fan Nickname: Emohawk for Tobias. Hawkward for Rachel/Tobias moments. KASU for "Katherine Applegate Screws Up/Screw-Ups", or the mistakes between books by the author and her ghostwriters.
Fantastic Racism: In addition to the commonly dismissive perspective the Andalites take to the Yeerks, the series gets some good mileage out of Tobias's attitude towards other birds. He calls Golden Eagles "nuts" (they occasionally hunt hawks) and is generally disdainful of seagulls and pigeons. There's even a debate as to whether or not this could count as racism by the other Animorphs.
Andalites tend to be like this in general. While they don't hate other species (except Yeerks) they generally see them as primitive and inferior
Yeerks are "slugs", Andalites are "grass-eaters", Taxxons are "bugs" or more commonly "worms", Hork-Bajir are "geniuses" and "bark-chewers", and humans are "monkeys."
The standard Yeerk-on-Andalite insult seems to be "Andalite filth!," while the inverse is "Yeerk scum!"
"Fantastic Voyage" Plot: In book #42, the Helmacrons take Marco hostage by invading his body. The Animorphs shrink down and go in after them.
Faster-Than-Light Travel: By means of Zero-space (Z-space for short), which is "anti-space." It shifts and reconfigures, meaning the time it takes to travel from one planet to another isn't consistent. Z-space is also where the Animorphs' excess mass goes when they morph creatures smaller than they are (as mass can't be created or destroyed), and, presumably, where they derive the mass for when they morph larger creatures. This also makes travel through Z-space dangerous, as that excess mass is physically present and can be crashed into.
Final Battle: A pretty epic one, too, although the main characters don't directly participate in it. (Jake even describes it as the "final battle.")
Final Speech: Hirac delest is an Andalite term for one's last thoughts or final words. It is a fairly common practice among Andalite warriors to record it just before their demise. The Andalite Chronicles takes this concept Up to Eleven, as the entire text actually serves as Elfangor-Sirinial-Shamtul's hirac delest.
Fire-Forged Friends: How the Animorphs became friends. Before the meeting with Elfangor, they weren't close - Marco and Jake were best friends, Cassie and Rachel were best friends, but Rachel and Jake, despite being cousins, weren't close, Cassie and Jake only barely knew each other (but still had a mutual-crush thing going), and Rachel and Marco only really knew of each other. Jake was the only one who knew Tobias much at all, having stopped him from being bullied a few times, and, of course, they had never met Ax. But, as Marco notes, after someone saves your life a couple of times, you tend to cut them a little slack.
First Name Basis: Most of the main characters. Out of the main Animorphs, only Jake and Ax's full names are ever revealed. The Pretender and The Andalite Chronicles hint that Tobias' last name is Fangor, but it's never confirmed. See No Name Given below for more on that.
Five-Token Band: Jake and Rachel are Jewish, at least on their fathers' sides, Cassie is black, Marco is half-Hispanic, Tobias comes from a very broken home, and Ax is an alien. (Although Jake and Rachel are at very best extremely reformative Jews.)
All the characters were Flanderized, actually, to a lesser extent. Cassie was the most notable (other than Rachel) - she goes from a slightly more moral person than the others to someone who couldn't stand to kill Visser Three. Note that her Flanderization was mostly reversed after book 45.
Jake was noticeably Flanderized as well - his leader angst goes from mild to extreme, until the last book, at which point he feels like Tom and Rachel's death was his fault and becomes clinically depressed.
The Flanderization was, really, the point. The war took whatever aspect of their personalities was most useful to the fight (bloodlust, strategizing, manipulating people, etc.) and forced them to exaggerate it until it ate the rest of their lives.
Foil: All over the goddamn place. All the main characters act as foils to each other to some extent.
Marco is the foil to Jake (taking orders vs. giving orders), Tobias (pragmatism vs. idealism), Cassie (pragmatism vs. moral relativism) and Rachel (subtlety vs. brute force).
Jake is the foil to Marco (taking orders vs. giving orders), Rachel (leadership vs. insubordination; they say this is what happens when two "strong" personalities mix), Tobias (confidence vs. insecurity) and Ax (leadership vs. loyalty to authority figures).
Cassie is the foil to Marco (pragmatism vs. moral relativism) and Rachel (peace vs. conflict).
Tobias is the foil to Rachel (peace vs. conflict), Jake (confidence vs. insecurity), and Marco (pragmatism vs. honor).
Rachel is the foil to Marco (subtlety vs. brute force), Jake (leadership vs. insubordination), Cassie (peace vs. conflict), Tobias (peace vs. conflict) and Ax (giving orders vs. taking orders).
Ax is the foil to Jake (giving orders vs. taking orders), Marco (pragmatism vs. "warrior ethics"), and Rachel (emotionalism vs. logic).
The Ellimist and Crayak act as foils to each other (life vs. death, the forces of good vs. the forces of evil).
Visser Three is the foil to Visser One (psychopathic, sadistic, irrational evil vs. pragmatic, intelligent, everyday evil).
Foregone Conclusion: All of the Chronicles books, to some extent, by way of being stories told in flashbacks about established characters.
The Andalite Chronicles is narrated by Elfangor, who died in the first book. His commanding officer is Alloran, the host body of Visser Three. Even if you didn't know either of these things before reading, the Framing Device is Elfangor transmitting his last testament telepathically to his ship minutes before he dies, and he mentions being responsible for creating the Abomination, Visser Three.
The Hork-Bajir Chronicles is about the invasion of the Hork-Bajir homeworld by the Yeerks. At the start of the series proper, all of the Hork-Bajir are enslaved by Yeerks.
Visser is about Visser One giving testimony about her invasion of Earth while on trial for treason. It is obvious from the series proper how successful she was.
The Ellimist Chronicles is the Ellimist telling a dying Rachel how he became the godlike being the main characters know him as.
Rachel (narrating): But even I have enough sense to know the words "we have to win" are the first four steps on the road to hell.
The Ellimist Chronicles begins and ends with the Ellimist visiting a dying Animorph. He admits that he did not cause him/her to be an Animorph, and that it was random chance. According to Megamorphs #4, this means that this can only be Jake or Rachel. It turns out to be Rachel.
Most of the information about Z-Space's finer workings comes from the books narrated by Marco. Marco's Dad is the first human to discover the existence of Z-Space and build a transmitter.
In the first book, and as seen in the fourth quote on the quotes page, Marco comments to Jake " You want to get into this fight against Yeerks? Fine. We'll see how gung-ho you are when it's your own brother you have to kill." Jake has to give just that order in the finale. It also foreshadows the fact that, for much of the series, Marco's mother (also a close relative) is Visser One's host body, as well as the fact that Marco has to (attempt to) kill his mother (although the time he pushed her off the cliff, she survived.
The cause-and-effect domino line in this series is staggering. Remember, while the kids' part of the story only lasts three years, the entire conflict lasts over two decades, with the kids only jumping in near the end. Much of what happens earlier in the war only has a real effect on the story as the war reaches its conclusion. What if the Skrit Na had never kidnapped Loren and Chapman? No Animorphs, no war on Earth period. What if Arbron hadn't been trapped as a Taxxon? Earth would've been successfully taken over by Yeerks.
What if a pubescent Jake had felt the need to act macho to impress his crush Cassie? Planetwide Andalite genocide and enslavement and an unstoppable Yeerk Empire.
There is something of a Running Gag with them forgetting that cockroaches can fly. Subverted once, where narrator remembers that cockroaches can fly and attempts to do so, only to remember that cockroaches can't fly well.
There's also a rather infamous incident in The Familiar where Future Cassie is thrown from a tower. Jake has to choose between saving her and saving the world, apparently because she's forgotten she can morph.
Four-Star Badass: General Doubleday. Though, as Jake notes, his rank isn't very intimidating to any of the Animorphs; "After you've stared down the likes of the Ellimist and Crayak, you don't quiver just because some guy has stars on his shoulder."
Framing Device: All of the Chronicles books. The Andalite Chronicles is presented as Elfangor's last testament (known by Andalites as a hirac delest), given in the final moments of his life. The Hork-Bajir Chronicles is told to Tobias by Jara Hamee sometime between books 13 and 23. Visser has, by far, the most in-depth one, switching back and forth between Visser One's memories and her present-day trial. Finally, The Ellimist Chronicles is narrated to a then-unnamed dying Animorph, indicating that at least one of them will die.
Freak Lab Accident: How the Ellimist became a godlike being. Having his consciousness spread across multiple advanced bodies, some remaining in space and some in Z-space while the rest was sucked into a black hole, allowed his consciousness to integrate with the fabric of the universe. However, he notes that while the odds of this happening once were astronomical, the fact that it happened meant that Crayak could replicate it.
Gambit Pileup: In Book #53 The Answer, Jake uses the Auxiliary Animorphs and the U.S. National Guard to distract Visser Three, so he can sneak above the Pool Ship. Or so Visser Three thinks. Actually, Jake is relying on him to believe that, so he doesn't realize that Jake and the other Animorphs are already aboard the ship, with help from Tom, who wants Visser Three dead himself, and plan on fighting him with the help of the free Taxxons. But, Tom decides to betray Jake to Visser Three at the last moment, which Jake saw coming and avoided dying with help from the Chee, who Tom and Visser Three didn't even know existed. Yeah.
Gender Bender: Pretty much all of the kids at some point: Rachel's eagle, acquired between books 1 and 2, is male, as is the grizzly bear that she acquired in book 7. Marco acquires a girl wolf in book 3, while Jake, Marco and Ax all become a female skunk in book 9, and Rachel and Cassie (along with the four boys) acquire a male polar bear in book 25. The only human example, however, is Tobias, who acquires Taylor, a human female, in book 43.
Genetic Memory: Howlers, though their memory is constantly tampered with by Crayak, to preserve their naiveté and maintain their usefulness as killing machines. Andalites also possess a genetic memory, though it's much more random and is only triggered as a near-death-experience; Tobias gains it after acquiring his uncle, Ax's, DNA.
It's also implied that the Yeerks have this to an extent.
Genre Savvy: Marco shows a strong indication that he knows he's in a fairly dark series with a rather sadistic author whenever he's being a Deadpan Snarker. Later in the same book, upon being told they're not comic book heroes, he makes the rather prophetic comment: "Yes, but I really really want it to be a comic book. See in a comic book the heroes don't get killed."
Cassie: "I wonder if there's a limit to how many morphs you can do."
Marco: "I guess we'll find out. Probably at the worst possible time."
Marco: Now I have a new superstition. Anytime I'm not worried, I worry.
Marco: I'm paranoid, sure. But that doesn't mean I don't have enemies.
Girls Need Role Models: Subverted. Initially, Rachel is the obvious choice as the feminist role model in the series (strong-willed, good-looking, personable, bold, courageous, capable in combat, etc etc), with Cassie acting as her meek best friend. However, by the end of the series, Rachel is miles away from a Mary Sue, her "bold and courageous" personality ultimately evolving into that of a sadistic action junkie. Cassie, on the other hand, while proven to be smart and capable, remains a relatively passive character uninterested in leadership qualities, stemming from her belief in nonviolence. Ironically, her empathic tendencies and ability to understand others makes her one of the best manipulators the team has...and she will use those abilities if need be. This makes her an atypical feminist character in that while she can take a more active role she simply chooses not to.
A Yeerk controlling Jake gets surprised and glares at Ax (Yeerks and Andalites are practically bloodsworn enemies). The reaction warns the Animorphs that something is wrong. The Yeerk does an okay job protesting his innocence until Ax moves to acquire Jake's DNA so he can play his role while the Animorphs make sure Jake isn't infested. As soon as Ax comes in contact with Jake's skin, the Yeerk yells out, "Get your hands off of me, you Andalite filth!" thus torching any chance he had of solving the situation with his secrecy intact.
Other than that, one of the really disturbing things about this series is that, for the most part, there is no Glamour Failure on the part of the Yeerks; their replacement and impersonation of their host is so thorough and effective that even their closest friends and family never notice the difference. There is a subtle change, though: Marco notes in an early book that "Tom just hasn't been acting like Tom" after the kids realize Jake's brother is a Controller. Similarly, Melissa notices that her parents, who are Contollers, always seem insincere. The Yeerks essentially rely on the fact that no human would automatically assume that a subtle change in personality would mean an alien parasite in their head.
Near the end of the series, there's a lot more Glamour Failure. For example, Tom will disappear for hours without giving an explanation. In one instance he mutters to Jake about how he's "preparing" for something. Justified in that by the end the Yeerks have amassed enough power to forget stealth and secrets, and are simply waiting for the orders for an open war.
God for a Day: Rachel was given the chance to become the ultimate fighting machine by Crayak. However such things are not much fun for a Blood Knight and it leaves only the satisfaction of sadistically snuffing out your enemies which is a road she doesn't feel comfortably going down when Crayak starting saying she is Not So Different.
Subversion: Visser Four rockets through the time stream, altering the results of battle to see to it that the human race is more cowed and easier to enslave. The book opens in a totalitarian alternate present with slavery still legal and women who "don't know their place" in reeducation camps, but no actual Nazis. During his travels he goes to D-Day to ensure a Nazi victory, but thanks to his previous changes, there never were any Nazis.
But they do see Hitler. Though tempted, nobody does anything to him since this Hitler is just a scared guy driving a jeep. Then Tobias's Hork-Bajir blade either slips or "slips." The question of which it was kinda hangs there unstated.
Goggles Do Something Unusual: During the David Trilogy, the Animorphs try to infiltrate the Marriott resort as seagulls, but a Human-Controller wearing sunglasses is able to stun them and other birds with his sunglasses from a distance.
Elfangor in The Andalite Chronicles. Also Arbron in the same, Aldrea in The Hork-Bajir Chronicles,Toomin in The Ellimist Chronicleswith the Andalite cavemen and Essam and, to a degree, Edriss in Visser. Those Chronicles books certainly did follow a formula, didn't they?
Also, Ax, to a degree. By the end of the series he's arguably more human than Andalite in terms of personality and habits.
This applies to the Chee as well after they used their holograms to disguise as humans.
Yeerks, though more of a case of "Neutral All Along":
Yeerks, like humans, aren't all evil. They simply have the unfortunate luck to be born puppeteer parasites, who's natural form is very much And I Must Scream. The only way for them to see, taste, build, basically be anything more than a slug was to take over a being that can do those things. On their home world, they have a symbiotic relationship with a clumsy sub-sentient humanoid, the Gedd, with the Yeerks essentially acting as interchangeable brains. Upon discovering that they were able to utilize better species as hosts... well...many humans would not be strong enough to pass up the chance at becoming a superbeing, either.
While most Yeerks, such as Visser Three, genuinely support the imperialist philosophy of conquest or are Just Following Orders, some Yeerks are part of a Yeerk Peace Movement dedicated to the creation of artificial, non-conscious host bodies (In an alternate future, the Yeerk Peace Movement becomes the Evolutionist Front, a splinter-cell terrorist group, albeit with similar goals as the YPM.) Even more startling: Some of the Yeerks who inhabit host bodies are children, who are given the choice between participation or execution.
It's implied that even the imperialist Yeerks are only like that because they've been spoon-fed Empire propaganda since birth.
Cassie: "They don't know any better. If you were raised since birth on Empire propaganda, you'd fight to take over Earth, too."
Taxxons are actually intelligent creatures who posses an unfortunate trait: They're constantly hungry. When they see an open wound they go insane with hunger, "it's like watching sharks react to blood in the water." On their homeworld, this is kept in check by a benign Hive Mind, allowing them to live peaceful and productive lives. When removed from this influence they are overwhelmed by their base instincts. Because of this, the Taxxons have willingly offered themselves into bondage by the Yeerks, in hopes that the Yeerks would be able to suppress their insane hunger. It didn't work. But the Yeerks are fine with that.
Good Cannot Comprehend Evil: The Pemalites were a race of dog people with no concept of violence or killing. As such were defenseless when the Howlers exterminated them.
Good Republic, Evil Empire: Played with a bit, as the Yeerks are clearly an empire and the Andalites a kind of republic, but the vast majority of Andalite government and military leaders the characters meet aren't much better than the Yeerks.
Oddly, while the Yeerk Emperor is chosen for life by the Council of Thirteen, the Council itself is democratically elected; meanwhile, the Andalite government is practically a junta; specifically, the Andalite civil government is apparently democratic, but it is implied that, over the decades-long Yeerk War, their military has (intentionally or unintentionally) usurped a large degree of informal autonomy.
Good Thing You Can Heal: Morphing heals injuries, meaning Applegate abuses the hell out of this trope. It becomes an issue when they enlist disabled kids as backup, and those who had merely been permanently injured get healed and now have to hide their returned mobility.
Gorn: The team's ability to heal any injury by morphing means Applegate was free to put them through as much horrific punishment as she wanted without permanently injuring them. Naturally, she got carried away at times.
Go Through Me: A quiet moment of awesome in #38: the Animorphs are fighting in the Yeerk pool, backed up against cages containing temporarily free human hosts. The hosts stand up and make a human barrier to keep the Hork-Bajir from just shooting through the cages; the Hork-Bajir haven't been ordered to kill hosts and they hold their fire.
Grail in the Garbage: The Animorphs first meet David when they discover that he's selling the Morphing Cube online without having any idea what he's got his hands on.
G-Rated Drug: Instant maple and ginger oatmeal is addictive to Yeerks, replaces part of their brain stem, eliminates their need for Kandrona rays, and drives them insane.
Gratuitous Spanish: Averted. Marco mentions knowing "about fifty words" of Spanish, and never uses them in conversation.
Graying Morality: It starts off as a typical children's sci-fi with the Yeerks as evil and the Animorphs, and by extension the Andalites, as the good guys. This doesn't stick.
One of the major themes of the series. It starts out as Black and White Morality, but The Departure turns the black into grey as we learn more about the Yeerks (though with Visser Three in charge, a very dark grey ) and The Hork-Bajir Chronicles turns the white into gray as we learn more about the Andalites.
The Greys: The Skrit Na, who like to abduct people and perform bizarre medical experiments on them for no discernible reason. The other characters note this but don't spend a lot of time trying to figure it out.
Growing Up Sucks: Especially when you're trapped in an interstellar war to save human freedom at age thirteen.
Groin Attack: Rachel does this to a male Controller once, and Loren does this to Chapman in the Andalite Chronicles.
Handshake Refusal: At the end of the episode where Tom and Jake are taken to the country for their grandfather's funeral longer than the Yeerk can survive, the Animorphs save the day by breaking Tom's leg so he gets sent back into town. Marco, who came up with the idea, offers his hand to Jake as a sign of all being forgiven (Jake had been dealing with the possibility that his brother might be finally freed), but Jake just lets it sit there.
Having a Gay Old Time: The phrase "hooking up" makes many appearances. In context, it just means "meet up," but the phrase has taken on quite a different meaning ten years later!
One of the perks of the morphing power. As long as you can survive the injury long enough to morph or demorph, you're golden. And since the morphs are based on DNA, not the physical condition of the target, a person can acquire a morph of an injured (though it still has to be living) animal and turn into it at full health. Several of the Auxillary Animorphs and Loren were crippled as a result of injury, not birth defects, so they were back in full health upon their first morph.
The Hork-Bajir can heal extreme wounds very fast, such as when Dak Hammee cuts his own head open, shows his brain to the Animorphs, and is able to close the wound simply by pressing the two sides of his cut flesh together. It's not like he isn't hurt from it, but it was clear that the injury was far from lethal, and a scar forms over the cut in moments.
Happy Place: When Taylor figures out that simply torturing Tobias won't work, she starts sending him to his Happy Place too, attempting to shatter his mind by jumping from pure pleasure to pure pain. It works, but Taylor is too far gone herself to notice. Although interestingly enough, you could also argue that she tries this method specifically because Tobias is sending HIMSELF to a Happy Place (albeit not a terribly happy one) in order to keep from breaking down. Up until that point, he'd been surviving Taylor's methods by hiding in the hawk half of his mind, which, being the brain of a wild animal, was much better at living with pain without suffering deep psychological damage than his human side was. That's why the Happy Place method was so effective- the hawk brain was good at dealing with pain, but it didn't know what to do with happiness, which isn't something that a hawk brain understands. The happiness was just too tempting for Tobias' human side, and it drew it out of hiding- at which point Taylor slammed down on the pain button again and wacky fun ensued.
Healing Factor: Morphing regenerates injuries, making the Animorphs and other morphers very, very hard to kill.
Heroic Vow: Two major ones. Firstly, the kids will never morph a sentient species without the individual's express permission. The other vow is a little more vague: The kids "fight Yeerks, but won't become them". This essentially means the kids agree to not use the same underhanded tactics Yeerks use (cold-blooded murder, ganging up on a single enemy, et cetera); this is so that the kids can try to maintain their morality while fighting a guerilla war in which they are hopelessly outgunned. The kids wind up breaking both of these vows.
Tobias counts for this one right from the very first book, The Invasion. During the battle under the school, he chooses to attack one of the Hork-Bajir ready to infect Cassie with a Yeerk. This in turn leads to him ultimately being trapped as a Red-tailed Hawk, permanently. He gets better, though. Sorta. Although the characters begin to wonder if it was intentional.
Hidden Depths: In the final story arc, Jake relinquishes command for a short period. When he becomes leader again, he's an absolute authority figure, and refuses to second-guess himself or let anyone else question his decisions, working from the standpoint that "a leader who shows weakness invites disaster". This ultimately leads him to becoming the most ruthless character in the series.
Erek was FDR's butler and coined the phrase "New Deal" in a card game. He also worked on the Pyramids and did Catherine the Great's hair. Elfangor also talks about his human friends "Bill" and "Steve" and their primitive ideas regarding computers.
Also, Mr. King was the one who suggested heat to Pasteur as a means to kill bacteria. Also, remember that painting of Washington crossing the Delaware? The kids go back in time and find out the river and the night were freezing. So not only did the kids see first-hand that Washington never posed like that, they directly state that if he posed like that in the middle of the night on the front of a boat crossing an ice-cold river, his soldiers would have thought he was a loon.
Hitler's Time Travel Exemption Act: Visser Four actually hoped to find Hitler and warn him of the Allied invasion on D-Day. Trouble is, thanks to the other ways he screwed up time, the Nazis are a combined French and German force, the invaders are all British, and Hitler is a Jeep driver, and as Marco points out, the "Nazis" don't actually appear to be Nazis anymore, and they can't even be sure the French/German alliance is the "bad guy". So rather than being of assistance, Visser Four is captured and imprisoned. Tobias still wants to kill him on general principle, but Cassie insists they can't because this Hitler hasn't actually done anything. Tobias later gets shot, and his blade "instinctively" slips and he kills Hitler anyway.
Hive Mind: Howlers. And Taxxons, through The Hive. Taxxons can voluntarily cut themselves off from The Hive, though, and they do when the Yeerks arrive.
The instant maple and ginger flavored oatmeal is only referenced in one book. In their defense, as Jake points out, battles that involve oatmeal will never really end up being historical.
Also, if Erek King could fight, the war would be over in about a week. Unfortunately, while he recognizes the necessity of the kids' cause, he himself finds violence to be too horrific to participate in (largely because his memories of the experience never fade) and is programmed to never commit any violent act. Everyone is severely traumatized by seeing Erek fight and kill, even Marco, who's unconscious for most of that battle. The carnage is so intense that it leaves Rachel a weeping, semi-broken-down wreck. It's also implied that Cassie was left traumatized by this as well and that it was a major factor in her decision to temporarily step down nine books later.
Honor Before Reason: The ordinarily-pragmatic Jake's approach to David in the David Trilogy is very much this, most likely to facilitate David's impending Face-Heel Turn.
Hopeless War: The Animorphs' objective isn't to win, but to at worst slow down the Yeerk invasion before the eventual loss and at best to slow down the invasion until the Andalite reinforcements arrive.
Holding Out for a Hero: While they try to slow the invasion on their own, the kids spend the better part of the series waiting for Andalite rescue. And waiting. And waiting. And waiting...
Played straight with Ax, who, in human morph early on, is just not quite right, thanks to a cocktail of misunderstanding human humor, taking directions too literally, and having access to taste buds. By the last third of the series, he's become much better at passing for human.
Completely averted by the Yeerks, as human-Controllers play their parts perfectly 99% of the time.
Humans Kill Wantonly: Ax becomes disgusted with humans during Megamorphs #3, when he sees the nature of human wars. He claims that though the Andalites had their own wars, they were never as pointless or sadistic as human wars were. He also claims that Andalites never deliberately killed children or committed genocide to other Andalites.
Both serious and not-so-serious examples. A prime example is the Yeerk designation of humanity as a "Class Five" host. They are intelligent and numerous but at the time of discovery possessed few natural or technological defenses against Yeerk infestation. They failed to count on human adaptability, though...
One notable example is Ax's observation that the Animorphs are using the morphing technology in ways the Andalites never even considered, in weaponizing it and acquiring dozens of different morphs for different situations, especially in so short a time. Most Andalites use it for subterfuge, and tend to specialize, only acquiring one or two animals over the course of their entire lives. That's not all there is to his observations, either. In the very first book from his point of view he noted that humanity went from basic powered flight to moon landings in a quarter of the time it took Andalites.
The sheer length of series entry on that page should say something about how much this trope plays a part in the series.
The first Visser One in the series had this to say:
"Humans have fought thousands of wars. Thousands! We as a race have fought a mere handful. They run straight into the bullets, Visser Three, again and again. Did you know that? They attack against insane odds. They defend what can’t be defended. Outnumbered, outgunned, surrounded, hopeless, they will still fight, fight, fight till they are each and every one dead. Something you might know if you stopped posturing long enough to learn something!" note Of course she then gives Marco the opposite speech later.
Ax, by combining DNA from all the kids, makes his own human morph. He's weird.
Also, an ant morphs Cassie. The results is so horrific that even Cassie thinks it should be euthanised. In the same book, a buffalo morphs Chapman; as buffalo have a sense of individuality and more intelligence than an ant, this doesn't go over quite as poorly.
Played with. The human kids spend the first arc of the series optimistic that the Andalites will come to Earth and take over the fight with the Yeerks for them. It turns out that the Andalites believe that humans aren't worth much overall, and decide that the best course of action would be to wipe out the entire human race so the Yeerks can't use them as hosts. The kids quickly up the ante in their missions after they hear that bit of news.
Also Zigzagged when Tobias led the free Hork Bajir to the valley, but was only able to because he was getting the directions from the Ellimist.
David, after spending his entire arc being a self-centered Jerk Ass. He thinks he's pulling one on Rachel but he's really being lined up for a Fate Worse than Death.
Also Visser One, in a way. You get the sense that his whole defeat is very humiliating for him; especially the fact that even after losing his enemies won't just kill him and get it over with. Visser One first abandons his host body then has to go through a war crimes trial, which Jake describes as "very un-Yeerkish".
Humorless Aliens: Andalites don't seem to understand the human sense of humor or its purpose, though Ax gets better at it as the series progresses.
100% Adoration Rating: All the Animorphs after the war, but Jake becomes a legendary figure verging on superhuman.
Hyperspace Is a Scary Place: The kids are, in one, instance, "pulled" into zero-space while in morph; that is, their consciousness was pulled into their extruded mass left in zero-space. Zero Space is not pretty.
Hypothetical Fight Debate: One instance had Jake and Marco arguing over Batman vs Spiderman, the point of contention being whether or not Spiderman's webbing would slide off Batman's body armor.