Animorphs

It's a normal day for Jake, Cassie, Rachel, Tobias, and Marco when suddenly a space ship crash lands near them. There they find a dying alien who tells them that the Earth is in great danger, that invaders known only as the Yeerks, are attacking Earth and plotting to take it over. He hands them a morphing cube with his last breath and thus gives them the power to morph into any animal that they touch. Now, the five young teens must brave incredible danger, with only their human brains and their animal forms to save the Earth from being taken over completely by the Yeerks.