Aliens have big eyes. 

They make noises like angry crows or
cars skidding. 

They smell kind of like detergent. 

Sometimes an alien might get a splinter and they would hop around like crazy.

They hate that.

Also, aliens cannot use spoons and forks, but they can dance pretty well.

Certain vegetables scare them, beets especially.

Don't ask me why.

Aliens do not smoke, but they won't give you a lecture if you want to light up.

Don't buy alien tapes or CD's because their music is totally lame.  It doesn't sound like anything except a
low hum. 

Oh, and they are delicious.