12 Days of Teen Lit: 5 Alien Beings!

Try Singing it.  Just once.  Really Loud: 

5 Alien Beings 

(Wasn't that Awesome?)

Now, on to the list! 

Adaptation by Malinda Lo. In the aftermath of a series of plane crashes caused by birds, seventeen-year-old Reese and her debate-team partner, David, receive medical treatment at a secret government facility and become tangled in a conspiracy that is, according to Reese's friend, Julian, connected with aliens and UFOs.

Alien invasion and other inconveniences by Brian Yansky. When a race of aliens quickly takes over the earth, leaving most people dead, high-schooler Jesse finds himself a slave to an inept alien leader--a situation that brightens as Jesse develops telepathic powers and attracts the attention of two beautiful girls.

The dangerous days of Daniel X  by James Patterson and Michael Ledwidge. Fifteen-year-old Daniel has followed in his parents' footsteps as the Alien Hunter, exterminating beings on The List of Alien Outlaws on Terra Firma, but when he faces his first of the top ten outlaws, the very existence Earth and another planet are at stake.

First day on earth by Cecil Castellucci. A novel about the true meaning of being an alien in an equally alien world.

Stuck on Earth . On a secret mission to evaluate whether the human race should be annihilated, a space alien inhabits the body of a bullied fourteen-year-old boy.