Cassie is the heart of the Animorphs and easily the best morpher, an Estreen.

General Information

Nickname(s): Tree hugger 

Gender: Female

Age: 13 - 16 (Series Time Span)

Personality: Calm, Caring, Peace-loving.

Battle Morph: Wolf

Best Friend: Rachel

Boyfriend: Jake


Cassie is the most compassionate member of the Animorphs, Rachel's bestfriend, and Jake's girlfriend. Cassie's family owns a farm that has been in the family since the Civil War, and has been remodeled into the Wildlife Rehabilitation Clinic; a sort of animal hospital for livestock and wild animals. The Animorphs generally use the clinic as their team "base" and form most of their plans there. Cassie's mother also works at The Gardens, a combination of a zoo and an amusement park. Most of the groups' morphs are acquired from The Gardens or the clinic.

Cassie has the reputation of being a "tree-hugger," due to her love for animals and lack of style. Her nature-loving personality isn't at all shallow though; Cassie has numerous moral struggles and questions about evolution, sentience in animals, the so-called "circle of life," and the morality of the Animorphs' fighting in the war at all. Though Cassie is willing to help fight the war when necessary, she desperately seeks a better way to win the war. At one point, Cassie decided to quit the team, as far as physical violence and using her morphing ability. She meets Karen, a Yeerk in the body of a five-year-old girl, and makes a deal to become a nothlit in a caterpillar's body when Aftran 942 agreed to leave the girl's body and never infest anyone again. Cassie escaped the morph when the caterpillar transformed into a butterfly (resetting the morphing clock, or natural morphing), but Aftran kept her promise.[1] Later, Cassie saves Aftran from Visser Three, who joined the Yeerk Peace Movement.

Though she is openly against most violence, Cassie was responsible for forming the plan to trap David and other victories on the Animorphs' side.[2] True to her dream to find another way to win the war, it was Cassie who allowed the Yeerks to get the Andalite morphing cube, showing the Yeerks that there was another way to see, hear, eat, and experience the other senses they were denied in their true forms than through infestation.[3]

The mention of "Father Banion" at the end of The Unknown (as part of Cassie's parents embarrassing her about Jake) implies that the family is Catholic.

Relationships with the other Animorphs

Jake: Jake and Cassie have crushes on each other right from the beginning of the series, and a romance slowly develops between them.  They finally kiss in book #26; in later books they both acknowledge the love they have for each other in their narratives, though they have not stated in outright.  Towards the end of the war, their relationship deteriorates and Jake loses trust in Cassie after she lets Tom take the Escafil Device.

Tobias: He is the closest in attitude to her, and they generally side together on group votes. Cassie's house is physically close to Tobias' territory.

Rachel: Cassie and Rachel are best friends, despite being complete opposites.  Their friendship becomes strained in later books, as Rachel becomes increasingly drawn to her warrior side and becomes impatient with Cassie's strong ethical convictions.

Marco: Although they are generally on good terms, Cassie and Marco are not close and don't spend much time together.  There is some personality conflict between them, as Cassie's morality is diametrically opposed to Marco's ruthlessness. However, at the end Cassie notes that she and Marco are really the only "true survivors" of the war and together they agree to try and break Jake of his depression.

Aximili-Esgarrouth-Isthill: Cassie and Ax don't interact often, although she does comfort Ax after Estrid leaves him. When Ax becomes sick with Yamphut, Cassie shows motherly concern for him before she performs life-saving surgery on him.[4] Ax feels hatred for her after she allows Tom to take the Escafil device, though they appear back on good terms later on.


Battle Morph(s): Wolf, Horse

Raptor Morph: Osprey

Morph Book Acquired
Horse The Invasion
Osprey The Visitor
Female Wolf The Encounter
Squirrel (Magilla) The Message
Dolphin (Monica)
Ant The Predator
Cockroach The Capture
Great Horned Owl
Humpback Whale (Great One) The Andalite's Gift
White Rat (Courtney) The Secret
Striped Skunk ("Mama")
Wolf Spider The Android
Spider Monkey (Unusable, Sario Rip morph) The Forgotten
Jaguar (Unusable, Sario Rip morph)
Parrot (Unusable, Sario Rip morph) The First Journey
Chameleon (Unusable, Sario Rip morph)
Human (Rachel) The Reaction
Racehorse (Minneapolis Max) The Unknown
Parrot The Escape
Hammerhead Shark
Mole The Underground
Mosquito The Decision
Tyrannosaurus Rex (Unusable, Sario Rip morph) In the Time of Dinosaurs
Caterpillar (May be unusable) - Temporary NOTHLIT The Departure
Butterfly (May be unusable)
African Elephant The Solution
Anteater The Suspicion
Baby Seal The Extreme
Polar Bear (Nanook)
Giant Squid The Exposed
Chimpanzee The Experiment
Eel The Sickness
Yeerk (Illiam)
Hork-Bajir (Jara Hamee) The Prophecy
Cockatiel The Proposal
Orca Whale (Swoosh) The Mutation
Cheetah The Weakness
Pit Viper The Arrival
African Cape Buffalo (Aka the Widow-Maker) The Hidden
Honeybee The Other
Hork-Bajir-Controller The Unexpected
Beaver The Resistance
Dragonfly The Answer
  • According to the Anibase, which can be downloaded here, Cassie has a total 46 morphs in the series.

Books Narrated By Cassie

  • #4 The Message
  • #9 The Secret
  • Megamorphs #1 The Andalite's Gift
  • #14 The Unknown
  • Megamorphs #2 In the Time of Dinosaurs
  • #19 The Departure
  • #24 The Suspicion
  • #29 The Sickness
  • Megamorphs #3 Elfangor's Secret
  • #34 The Prophecy
  • #39 The Hidden
  • Megamorphs #4 Back to Before
  • #44 The Unexpected
  • #50 The Ultimate
  • #54 The Beginning


  • Out of all the members the Ellimist planned to become an Animorph, Cassie had the most importance.
  • She is more talented at morphing than the others.
  • She has the unconscious ability to unravel any alternate/parallel universe/timeline.[5]
  • It is noted by Ax that Cassie could easily become a professional Estreen, one who morphs as a form of art, due to her inherent skills.
  • All of the models for the Animorphs featured on the front and inside cover had been changed since the series began, mostly because the original kids had grown up and moved away to college (since book 41). Only Cassie's model (Biko) remained close enough to still model for Animorphs. And of course Ax, who is actually just a cardboard cutout.
  • In The Departure, the naturally-occurred morphing timer-reset exception (That Cassie uses at the end of the book) is the second morphing glitch that is shown in the series. The first one being shown in #12: The Reaction, where it is revealed that an animal cannot be acquired if you are allergic to it. These exceptions never occur, nor are exploited in any way, in the series ever again.
  • In The Prophecy, Aldrea possessed Cassie's body temporarily to find a Yeerk base on the Hork-Bajir homeworld.
  • Her family is the first to leave when the Animorphs leave to hide in the Hork-Bajir valley with the exception of Marco.
  • In the Animorphs television series, Cassie's battle morph was a horse, as opposed to her wolf morph in the books.
  • In keeping with her non-violent nature, Cassie is the only Animorph who lacks a unique battle morph; she typically assumes a wolf form when required to fight, which the entire team acquired while investigating Yeerk activity in the mountains.
  • In 1999 three different Animorphs toys of Cassie were made. The larger one sold in stores turned into a wolf, and the smaller one was part of a Taco Bell children's meal promotion and turned into an anteater. She was also a part of the set of combiner Animorphs which turned into a Tyrannasaurus Rex.
  • Cassie is the only original Animorph not to accompany the group on the mission to rescue Ax at the end of the series, and possibly the sole surviving original Animorph after the series' end.
  • In the TV series, it's Cassie who's allergic to crocodile DNA, not Rachel. Also, unlike Rachel whom would transform into random animal several times when the allergic symptoms shows up, Cassie only suffer partial transformation on random parts of her body instead.