Alien is a broad, subjective term, often referring to species outside one's own planet, but it could be applied as a noun or an adjective, for any entity, object, place or practice which is not familiar. For example, people on Earth who live in other countries illegally are known as "illegal aliens", despite not being from another planet. Indeed, when Brian and Sophie first told Mel and Lucy that they were aliens, Lucy suggested they were illegal aliens from Canada. (Aliens Go Home)
When referring to entities, it was used for sentient organic creatures. Usually, this means entities which are not native to Earth and were "alien" from the viewpoint of the human race. However, to any species not native to Earth, a human would be alien. Indeed, Sophie, a Valuxian, once referred to her human foster children as a bunch of "lovable, two-eyed alien mutants." (The Wedding)
Species outside of EarthEdit
- This section lists species that originate on a planet other than Earth.