The Xenophile

Xenophile: a person who likes foreigners or things foreign [from Greek, from xeno- + -phile]. And by foreigners, we mean aliens. And not just humans who live in another country, either.

Aliens can be Intrigued by Humanity or a Fantastic Anthropologist, but what about the inverse - when a human character is obsessed with everything alien? This is often an evolved Naive Newcomer character in Speculative Fiction, and serves the same function in being a go-between and (sometimes literal) translator between a strange alien culture and the reader/viewer. Unlike a Naive Newcomer, however, the Xenophile doesn't need another character to tell him or her about the alien culture we meet - they can provide all (or at least, most) of the exposition themselves, cheerfully and enthusiastically! In fact, they're so enthusiastic they probably have neglected their relationships with their fellow humans. In addition to appearing in Science Fiction, this trope can also appear in Fantasy literature where a human character is enthusiastic about non-human races and cultures.

Note, This is not about a character who is attracted to aliens in another way... there's a different trope for that, although the two can easily be combined. Contrast Aliens Are Bastards. Also contrast Absolute Xenophobe. Again, aliens-liking-human-culture examples are a different trope and belong in Intrigued by Humanity or Fantastic Anthropologist. Compare Nightmare Fetishist; if the aliens are weird enough, both can apply to the same character. Compare Admiring the Abomination, where a character (often The Smart Guy) reacts to an alien threat with both excitement and fear.

Anime and Manga

 * The eponymous character from Haruhi Suzumiya.

Film

 * Ellie Arroway from Contact, both the book and the movie - at least when it comes to the idea of aliens and how to make contact with them.
 * Several main characters in Avatar are this to some degree.
 * In Enemy Mine, a human and a Drac pilot who are on opposites sides of an space war learn to set aside their racial and political differences to survive on a hostile planet. They start out trying to kill each other, but become good friends.

Literature

 * Bren Cameron of C. J. Cherryh's Foreigner series of books. Meant to be an envoy/translator from the human government to the native aliens, he essentially defects to the alien side.
 * Arguably, the Pevensie siblings from The Chronicles of Narnia become this.
 * Considering they number MANY nonhumans as friends, it's definite.
 * Willis E. Davidge, from Barry Longyear's The Enemy Papers turns out this way, getting a thorough education in Drac culture after being stranded on a ice planet with a Drac for quite a while. Note that he and the Drac were fighter pilots trying to kill each other in a war between the two species.
 * A few different characters in Larry Niven's Known Space books. Beowulf Schaeffer and Louis Wu come to mind. At least one of them explicitly referred to himself as a xenophile.

Live-Action TV

 * Many of The Doctor's companions seem to end up like this, so caught up with time travel they don't want to go back to their own time.
 * Daniel Jackson of Stargate SG-1, seemingly much more at home interacting with the many different cultures and races he's met through the Stargate than he ever is on Earth. He is an anthropologist, after all.
 * Several human, alien-wannabes in Earth: Final Conflict and Alien Nation.
 * Some among both Minbari and Humans are starting to become interested in each other's cultures in Babylon 5 though many remain resentful.
 * Jadzia in Deep Space 9 gets along with Ferengi, humans, and not least klingons.
 * Sisko meanwhile seems to love Bajoran culture to the point that he decides to build a house there.

Tabletop Games

 * "Xenophilia" is one of the possible disadvantages in GURPS (applying to anyone exotic, not just nonhumans). It's a disadvantage because it makes you trust potentially nasty creatures more than you should.
 * Warhammer 40,000: this is something the Inquisition works very hard to avert. Many citizens are attracted to the Tau's "Greater good" philosophy and occasionally less brutal treatment of its own citizens, while a very small amount of the Adeptus Mechanicus consider the Necrons holy warriors (it doesn't help that the Omnissiah is possibly the Necron's own omnicidal deity).

Video Games

 * Yeoman Kelly Chambers in Mass Effect 2 is thoroughly fascinated by all aliens, which is rather untypical for a member of the pro-human extremist organization Cerberus.
 * However, she says that pro-human does not necessarily mean anti-alien.
 * In Galactic Civilizations II, when culture suddenly booms it's credited to/blamed on the Xenophiles (Depending on whether your planets are deep in someone else's territory, or theirs are in yours)