[Nods.] Aliens more along her lines, yeah. Other planets and such, usually a completely different biology. Never encountered anything exactly like Selendis though.
The Doctor is an alien. Looks human, but he's got at least two hearts, and very likely changes his face as he ages. Likes to visit humans though.
And aliens can have more advanced technology and can come to Earth even though humans can't leave by my time. And usually they try to keep a low profile, I think.