Due to the fact that some tropes' very names are spoilers, all spoilers will be unmarked.
The Animorphs
Tropes that apply to all of them
- Adaptational Angst Downgrade: Thanks to the Chee giving them therapy, they're less trapped in cycles of trauma.
- Named by the Adaptation: Only Jake's surname was revealed in canon, though Rachel's surname being Berenson is common fanon.
Toby-Sirinial-Sky (née Tobias Calladan) & Elhariel
The first point-of-view character. Toby was lonely before meeting Elfangor, but eventually comes to bridge the gaps between the various aliens races. Their daemon Elhariel settled as a European storm petrel prior to the beginning of the series. For most of the series, Tobias is considered male. In Split-Hearted, they realise they're non-binary and change to she/they pronouns; then in The Presence of Justice, they change their name to Toby.
- Adaptational Gender Identity: As far as we know, Tobias was cis male throughout the entirety of Animorphs.
- Adaptational Nice Guy: The petulant self-centered aspects Canon Tobias sometimes shows when talking to Hork-Bajir are absent in Toby, as is Canon Tobias's rejection of the concept that there are innocent Yeerks. In general Toby is less reserved, more pro-social, and willing to reach out to people of many species, probably because they're so much less isolated in this series.
- Child of Two Worlds: In The Herdmoot, Toby is one of the feshlaths between humans and Andalites.
- Meaningful Rename: Tobias changes their name to Toby in admiration of all Toby Hamee has done, and their schwescor (a Great Gardens Andalite's third name, which refers to the place they took their first steps) from "Canada" to "Sky" because they renamed themself on the Pool ship with Sky Hive.
Jake Berenson & Merlyse
The Animorphs' leader. He's in a threesome with Marco and Cassie. His daemon Merlyse settles as a whiskeyjack at the climax of Welcome Home.
- Kill the Ones You Love: Merlyse settles when he chooses to send Tom (potentially) to his death, since whiskeyjacks are known to drive their siblings out of the nest so they have enough resources to survive the winter. Subverted in that Tom doesn't die.
- My God, What Have I Done?: At the climax of Welcome Home, Tom secretly follows the Animorphs and Toby's forces to a mission to free some Hork-Bajir from a Yeerk facility. When Jake realises this, he orders Tom to stay behind, pose as a Hork-Bajir-Controller, and put the facility into lockdown while everyone else retreats... and immediately regrets it when Merlyse settles as a whiskeyjack, a bird known to kill its siblings.
- My Greatest Failure: He feels a lot of shame over letting Tom become a nothlit, and lying to everyone that it was an accident.
Rachel Berenson & Abineng
Jake's cousin and Toby's girlfriend. Rachel is haunted by violent intrusive thoughts throughout most of the series. Her daemon Abineng settles as a sable antelope at the climax of The Cowardice of Lions.
- Kill the Ones You Love: She has to kill one of her former friends, who's now a controller, in The Abyss in order to save Mr. Tidwell.
- Spared by the Adaptation: Since Tom is freed, the Yeerks don't get the morphing cube, and she has more of a will to live, she never has to go on a suicide mission and thus survives the war.
- Symbiotic Possession: Putting Down Roots is about her coming up with the idea to have Toby morph a Yoort and infest her to help her when she's feeling stressed. Then she starts morphing a Yeerk and doing the same to Toby.
Cassie Clark & Quintavion
Jake's girlfriend and Rachel's best friend. She's the most manipulative of the Animorphs; she comes up with the plans to kill David by impersonating his parents to lure him into a trap, and to change Estrid's quantum virus from one that will kill all the Yeerks to one that will make them unable to control hosts against their will. She's also in a threesome with Jake and Marco. Her daemon Quintavion settles as a vampire bat at the climax of The Cowardice of Lions.
- Adaptational Angst Upgrade: In canon, Cassie had the fewest problems in her personal life. In this series, she feels a lot of guilt about coming up with the plan to kill David, and in Welcome Home, her mother gets taken by the Yeerks because she couldn't evacuate her in time.
- Bat Out of Hell: Defied. Cassie is horrified at first when Quincy settles as a vampire bat shortly after the Animorphs kill David, but her dad tells her that vampire bats are altruistic despite having to do harsh things to survive.
Marco López Chen & Diamanta
The son of Eva, Visser One's host. He's currently in a threesome with Jake and Cassie, and is on medication for PTSD for much of the series. His daemon Diamanta settled as a timber rattlesnake in The Bright Clear Line.
- Mind Rape: In The Cowardice of Lions, David ties Marco up in his closet and touches Dia, which Marco describes as feeling like David is licking his brain. He's shaken up by this for the rest of the series.
- Snakes Are Sinister: Well, they're seen that way, especially venomous ones. After Dia settles, Marco can no longer convincingly play the harmless, clueless kid.
Aximili-Esgarrouth-Isthill
Elfangor's younger brother, Loren's brother-in-law, and Toby's uncle. He's one of several Andalites stranded on Earth. His guide tree is called Firi Dria, which blooms at some point before Destroyer of Worlds.
- Aliens Love Human Food: It's downplayed a bit, and he learns more about it instead of just cramming things into his mouth, but Ax still sure does enjoy eating human food.
- Heel Realization: He eventually becomes disillusioned with the extreme measures the Andalites will go to in order to defeat the Yeerks.
- Nice Job Breaking It, Hero: Since he destroys Estrid's lab, she doesn't have a chance to test the quantum virus more, so it kills more Yeerks than she intended.
- Pay Evil unto Evil: During The Abyss, Ax, suffering the effects of being underground and in a bad situation, starts attacking Estrid. After she deliberately infects the Aftran Plisim Pool with her virus he tries to kill her, then when prevented destroys her lab.
Loren St. Clair & Jaxom
Toby's mother. She lost her vision and most of her memories in a car accident years ago, but morphing heals her in Carry On Wayward Son. However, she still continues living as a blind woman so she can interact with her friends thanks to a hologram made by the Chee. Her daemon Jaxom is a zebra druiker.
- Adaptational Early Appearance: Loren first appears in Self-Defense, set shortly after the events of book 15, a whole 34 books before she appeared in the main series in canon.
- Dead Person Impersonation: When Loren joins the team, the Yeerks believe she's David and call out to "him", since they know he joined and could be tempted and don't know he was killed. Loren automatically makes some effort to play into this, but a few fics later Taylor pointedly asks her what David's mother's maiden name is.
- Decomposite Character: Jaxom is her Handy Helper instead of Champ, who's now a regular dog owned by the Chee.
- Handy Helper: After she goes blind, she learns how to go into "four-eye" and see through Jaxom's eyes.
- Honorary Aunt: She's technically Ax's sister-in-law or taf ratheen (female relative by love), but he calls her his aunt.
- Obfuscating Disability: The morphing power repairs her eyes and restores her sight, but she continues living her life as a blind woman for months.
- Shapeshifter Mode Lock: In A Place to Stand's alternate timeline, she became an Andalite nothlit to be with Elfangor.
- Shout-Out: Jaxom is named after a character from Dragonriders of Pern.
- Sixth Ranger: She joins the Animorphs early on in the series, and unlike the other humans that gain the morphing power later, she becomes a main character.
- Team Member in the Adaptation: The series really starts to diverge from canon when the Animorphs realise that Loren could be a potential ally, and she ends up joining them.
- Xenafication: Canon Loren has a strong introduction in The Andalite Chronicles, and when she's reintroduced she risks her life to save Tobias, but then she majorly fades back. Daemorphing's Loren becomes a full Animorph about halfway through the series, fully participating in their actions.
Animorphs' family members
Tom Berenson & Delarayne
Jake's brother. His daemon Delarayne settled as a Thompson's gazelle at some point while he was a controller. Marco comes up with the plan to free him in Abel or Cain, and he goes to live in Kref Magh. In Welcome Home, he's given the morphing power... but he blows his chance to be a real Animorph when he becomes a Hork-Bajir nothlit at the end.
- Adaptation Relationship Overhaul: He's close friends with Ax, Tobias/Toby, and the free Hork-Bajir; he never had the chance to interact with anyone of his own volition in canon.
- Adaptation Species Change: He never even acquired a Hork-Bajir morph in canon.
- Brought Down to Badass: He may have lost his morphing ability, but Hork-Bajir are more than capable of fighting. He helps to capture the Pool ship in The Presence of Justice.
- Going Native: After living with the Hork-Bajir for months and not getting along with the other human refugees, Tom learns their language and is accepted into their culture. And then he becomes one of them.
- Mirror Character: Tom has a lot of things in common with Tobias/Toby; both of them become nothlits while trapped in underground Yeerk facilities, get along well with the free Hork-Bajir, and have blonde human girlfriends whose names begin with R. All of these traits apply to canon Tobias as well, but Tom has a completely different role in the story.
- Shapeshifter Mode Lock: Jake orders him to pose as a Hork-Bajir-Controller and put an underground Yeerk facility in lockdown; he doesn't have a chance to demorph because he'd risk being killed or infested.
- Sixth Ranger: Subverted; he only gets to go on a mission with the Animorphs once, and it's against Jake's orders.
- Spared by the Adaptation: Since the chain of events that ultimately led to Rachel biting his head off never even got started in this universe, he survives the war.
- Throw the Dog a Bone: For much of the series, Tom is only slightly better-off than in canon. He's freed, sure, but he has bipolar disorder brought on by years of brain damage, regularly gets into fights with the other human refugees, and accidentally-on-purpose becomes a nothlit. At the end of The Cost of the Fight, though, he gets a girlfriend. Even Jake is surprised to see him be happy for once.
Other humans
Melissa Chapman & Ververet
Rachel's friend from before the war. She was infested by a Peace Movement Yeerk at some point, who then sacrificed their life so she could escape to Kref Magh in Abel or Cain. In Destroyer of Worlds, she gets the morphing power. In The Abyss, she refuses to kill a Hork-Bajir-Controller, which allows the Yeerk to infest her and leak the Animorphs' secrets. The Hork-Bajir former-host then kills her. Her daemon Ververet settled as a cabbage white butterfly at some point early in the series.
- Adaptation Relationship Overhaul: She never forgives the Animorphs for torturing Chapman in Abel or Cain, and she doesn't understand why they have to do such harsh things, so her relationship with Rachel is strained.
- Death by Adaptation: As far as we know, she survived the war in canon.
- Plot-Triggering Death: Her infestation and subsequent death causes everything to go south in The Abyss.
- Sixth Ranger: She's one of the humans who gains the morphing power in Destroyer of Worlds when the Animorphs realise they need more help.
Ruby & Keowe
An Original Character. Ruby is a homeless transgender woman who the Yeerks were planning to sever from her daemon Keowe (a rainbow scarab) in The Guided and the Lost, but fortunately the Animorphs saved her. As of the end of The Cost of the Fight, she and Tom are an item.
- Disposable Vagrant: The Yeerks were experimenting with severing humans from their daemons in order to make them easier to control, and tested it out on homeless people. Ruby was the only one to make it out alive.
- Tough Beetles: According to the author in a comment
, Keowe settled as a rainbow scarab because they're very adaptable and hardy, and she's survived the worst life can throw at you and came out relatively unscathed.
Other Andalites
Estrid-Corrill-Darrath
Alloran's daughter. She came to Earth as part of a crack team to kill the Yeerks with a quantum virus, but Cassie convinces her to change it to one that would remove their ability to control hosts against their will instead. Mr. Tidwell and Illim stop Ax from killing her in The Abyss, and become Estrid's adoptive parents shortly afterwards. Her guide tree, Surra Erf, blooms during The Herdmoot.
- Adaptational Villainy: Estrid is portrayed more harshly as her canonical willingness to create a genocidal virus that might jump species is more fully examined and condemned and her doubts and discomfort about doing so are nonexistent, not to mention the usual suite of Andalite -isms that applies to her. She also decides to secretly clone Toby For Science! She gets better.
- My God, What Have I Done?: After realising that her quantum virus killed hundreds of baby Yeerks in The Presence of Justice, she tries to commit an honour suicide, but Ax stops her. Instead, she decides to atone.
Gafinilan of Theresh
An Andalite from the Ixilan culture, who was a famous warrior and has a terminal illness called Soola's Disease. Ixilans revere the disabled as spiritual guides, called tzeraf. At the end of Welcome Home, the Yeerks find and capture him; after Alloran is killed in Destroyer of Worlds, he becomes Esplin 9466-Prime's new host.
- Adaptation Name Change: In canon, there's nothing to suggest that Gafinilan-Estrif-Valad isn't his real name, but it's revealed in Shattered that he made up his last two names to fit in with the Great Gardens' military.
- Shapeshifter Mode Lock: After Esplin infests Gafinilian, he forces his host to morph Alloran for over two hours so he doesn't die of Soola's Disease.
Alloran-Semitur-Corass
Esplin 9466-Prime's former host and Estrid's father. Shortly before The Guided and the Lost, he was severed from his guide tree Henga Sholeth. His brother Arbat kills him in Destroyer of Worlds.
- Death by Adaptation: He survived the war in canon, and was responsible for getting the Andalite Fleet to listen to the Animorphs. Since he's dead in Daemorphing, the Animorphs have to find a different way to get the Andalites to surrender.
- Demoted to Extra: All of his uninfested scenes are skipped over, and he dies long before he has a chance to be freed.
- Related in the Adaptation: While him being Estrid's father is a popular fan-theory, it's never been officially confirmed.
Hork-Bajir
The species as a whole
- Always Lawful Good: Since all Hork-Bajir hosts are involuntary, there's no risk of them betraying the Animorphs to the Yeerks. Marco mentions this when he's arguing in favour of giving the free Hork-Bajir warriors the morphing power.
- Aura Vision: Hork-Bajir can see the Dust, which they call hrala. The Arn created them with this ability partly to maintain Dust creation on their homeworld, and partly because physical anchors are a burden.
- Eloquent in My Native Tongue: Most Hork-Bajir have an imperfect understanding of English and a better grasp on Galard and their own languages.
- I Thought Everyone Could Do That: Early in the series, they're confused when humans say they can't see hrala.
- You No Take Candle: Discussed. The Hork-Bajir aren't very good at English as in canon, but here it's explained that they have a hard time learning it and apply the grammar of their native creole language, which has no pronouns or tenses.
Kalij (née Toby) Hamee
The first Hork-Bajir not born into slavery for generations, and a Seer at that. She used to be the leader of Kref Magh, but the other Hork-Bajir realised this was putting too much stress on her, so she stepped down to only be their leader in battle. Then in The Presence of Justice, she changes her name to Kalij and steps down from all leadership positions.
- Adaptation Relationship Overhaul: She claims Tom is like a brother to her. She never even acknowledged his existence in canon. And while she respected the Animorphs to the end in canon, she has a major falling-out with them after their secrets get leaked in The Abyss.
- An Alien Named "Bob": Toby changes her name to Kalij because she wants to make her Hork-Bajir identity clear, and didn't like having a human name.
- Meaningful Rename: "Kalij" was the name of her mother's home valley.
- Took a Level in Jerkass: Toby in canon has hints of a desperate, ruthless mindset, but is always exactingly polite and deferential, making careful statements that gently suggest awareness of how the Animorphs value humans more than Hork-Bajir. Toby/Kalij in Daemorphing is a main character and that desperate mindset is at the fore, as is resentment about the Animorphs' priorities. Eventually the other Hork-Bajir stage an intervention - as the valley's seer, she's had to take up so much responsibility in such a stressful situation that she's started to act harshly even when it's not warranted.
