extraterrestrial beings

David's attempts to control the other Animorphs threatens to break up the group.

Cassie, one of a group of young people who has been given the power to transform into an animal in order to help fight an invasion of the alien Yeerks, decides she is tired of the battle, but she realizes she cannot quit just yet when a human-Controller named Karen learns her secret.

Tobias, trapped in animal form after morphing into a hawk, agrees to help save two Hork-Bajir from the evil Yeerks in exchange for his humanity.

A young bear helps a family of aliens return home. At various points in the text the reader is asked to guess what belongs in the picture.

Investigate the world of real-life monsters--dinosaurs--and read reports of aliens on Earth.

Professor Xargle's class of extraterrestrials learns about the physical characteristics and behavior of the human baby.

Describes how alien monsters have been imagined in books and movies and examines real creatures in nature that resemble or may have served as inspiration for them.

Marco is a reluctant Animorph, having been given the ability, along with four other friends, to change into animal forms by an Andalite prince, an alien who wants help in stopping an invasion of the enemy Yeerks, but when he discovers that his mom, who he believed was dead, has been taken over by the Yeerks, he finds a reason to fight.

Cassie believes her strange dreams are just a side effect of having been given the alien power to morph into an animal, but when she learns that Tobias has been having the same dreams about the ocean, they realize someone is issuing a call for help.

Jake and his friends are given the power to morph into animals by a dying alien who tells them the Earth is under attack by the invading Yeerks, and they are called upon to test their new abilities almost immediately when they learn that Vissar Three, deadliest of the Yeerks, is after them.