In Animorphs there seems to be a lot of aliens. Not as much as Star Wars, but we know of some twenty extraterrestrials. What is really nice is how Animorphs tries to be so realistic about the aliens. We have half scorpion/half horse/half man creatures (yes, I know there are three halves) called Andalites, parasitic slugs called Yeerks, aliens who spin cocoons and metamorphosize (like caterpillars) called the Skrit-Na, and many more. None of these are completely humanoid, and not all of them have even remotely the same life styles, like aliens in Star Wars. K. A. Applegate has done a superb job at creating a realistic universe full of a variety of species.

An interesting fact that you might want to know is that according to K. A. Applegate, the Skrit-Na are the aliens who fly around in saucers and take people away for medical experiments.