Animorphs

Marco, one of a group of young people who have been given the power to change into an animal in order to fight an invasion by the alien Yeerks, decides to check things out when his old friend Erek begins behaving oddly.

Ax and the Animorphs become trapped in Zero-space after morphing into mosquitoes in order to slip past some Yeerks. They are rescued by an Andalite scout ship and Ax must decide whether to stay with his own people or return to earth.

Jake and the other Animorphs have discovered a Web page that discusses how to conquer the Yeerks, but before they can trust anyone they have to determine if it is for real or if it is a trap.

Rachel and her friends run into a dying alien who gives them the power to morph into any animal they touch, placing the responsibility of saving the Earth from a silent, deadly attack completely in their hands.

When the Animorphs discover some strange happenings in the woods behind Cassie's house, they must stop Visser Three before he can destroy Ax's feeding grounds.

Tobias has stayed in his morph too long and must now live out the rest of his life as a hawk, but that does not keep him from contacting his friends and continuing the fight against the Yeerks, a race of hostile aliens that are invading and controlling the brains of humans.

Cassie, one of a group of kids who have been given the power to transform into animals in order to fight an invasion of the alien Yeerks, leads her friends into yet another mission when she discovers the Yeerks are trying to access Zone 91, the most secret place on Earth.

The Animorphs, a group of young people who have been given the power to change into animals in order to fight an invasion by the alien Yeerks, discover a new weapon against the aliens, but it means another trip to the Yeerk pool.

David, the newest Animorph, is not what he seems to be.

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