It's a common pet peeve among sci-fi fans: why do aliens always seem so undeniably human? Shouldn't a strange new consciousness from a far-away world seem more alien? And not just in looks - we've written about human-looking aliens before - but in motivations and behavior as well.

For instance, there's no reason to assume that an alien species would look like a human with a weird forehead. But there's also no reason to assume that aliens would have a human-like conception of property or of societal connection or even of self.

While what seems to be a majority of science fiction relies very heavily on making their aliens as behaviorally human as possible, there are a few aliens in the cannon that challenge our perceptions of aliens and what a true other might actually be like. Here are some examples of truly alien aliens (each include some spoilers).

Solaris

In one of the only common features between both film versions of Solaris and the original novel, one of the main objects of the story is to present a truly "other" alien. In Solaris, human scientists have stumbled upon a planet that seems to be covered in a living ocean. So, they attempt to communicate with it.

And the "ocean" communicates back in the only way it knows how: by conjuring up living manifestations of the deeply hidden tragedies and shames of the scientific crew. The films hint at what is the novel's focus: the sentient oceans are so alien from humanity that its attempts to communicate look more like torture. All three versions leave the audience with no clue as to what the sentient oceans actually want. And that's a lot more realistic than clear communication between two wildly different species.

The 456

The motivations of the 456 in Torchwood's Children of Earth miniseries are a lot clearer: they just want Earth's children for what appears to be a very gruesome narcotic-like use. But what makes the 456 so great an example of an alien species is that this use is never clear, and humanity is in no position to investigate the aliens.

It's another common misstep in alien stories: unlocking the biological or scientific secrets of the alien proves the necessary step to defeating them. In this story, the alien remains callously and disturbingly other throughout. It's like "To Serve Man" with a decidedly Lovecraftian twist.

The creature from Midnight

In the Dr. Who episode "Midnight," we see that in science fiction stories, you don't always need a malicious alien to find a villain. The alien in this case is certainly creepy, and its "voice stealing" method of communicating makes the viewer squirm, but in the end, the ones that we fear the most are not aliens, but other humans.

And that is what makes this, along with Children of Earth, such a great alien story: no matter what the extra-planetary life is, the much more frightening thing is the paranoia and fear-induced violence that this alien consciousness causes.

Rama

While Rama in Arthur C. Clarke's Rama series is actually a place, it reveals another misstep in most alien portrayals. When humans land on Rama and begin exploring, they are struck by how strange the place is. The "buildings" don't appear to actually be buildings, the "cities" are apparently uninhabited, and the sheer scope and engineering of the place betray a fundamental flaw in any human-assumption-based analysis of the place.

While this unknowable other concept gets shelved a bit in the sequels to Rendezvous with Rama, the first book ends as it might in reality: the craft moves on, and humanity is no wiser than before. Rama remains a foreign thing, even after all is supposedly "revealed."

(From this short film based on the book Rendezvous with Rama)

The Buggers and the Piggies

Finally, in Orson Scott Card's Ender's Game, and maybe more so in its sequel, Speaker for the Dead, we see two new alien races that eventually challenge humanity to tolerate and maybe even love something truly other. The buggers start the story as the frightening antagonist, but it's revealed that their acts of aggression were really attempts at communication. The piggies, on the other hand, seem wild and unpredictable at first, but their horrific acts were really ceremonies of great honor.

The reality of these books, though, is that, when all is said and done, the humans in these stories find the humanity in an inscrutable other. They prove to us that something menacing and indifferent and entirely alien can sometimes become almost human. And even if that means humanizing the aliens slightly, it's a feat that's far more impressive than getting us to sympathize with blue versions of ourselves.

Says Fincher:

“It looks like it’s not going to happen. There’s no script and as you know, [star Morgan Freeman’s] not in the best of health right now [after an August car accident]. We’ve been trying to do it but it’s probably not going to happen.”

The veteran actor had been attached to the project in various forms for roughly eight years now. And when previously interviewed, it appeared as if Fincher had been giving the execution of the pic great thought:

“It’s probably technologically within striking distance right now. That was always the thing: You couldn't afford to build these things as sets. It’s just too huge.… I think it’s more along the lines of motion-capture.”

Like the curious beings with their cryptic motives at the helm of the Rama, it now looks like we'll never quite know what really could've come of this long-anticipated movie.

Barbarella:
In 2007 Dino De Laurentiis was going to produce with Robert Rodriguez as the director. Rodriguez wanted his lady-love Rose McGowan to star as the sexy space cadet Barbarella. But Universal was not enjoying the casting move and didn't want to front the cash. Could McGowan pull off "sexy nubile blonde" as well as Jane Fonda? This April McGowan spilled that the project was still on (with her in the lead) and that a bunch of pre-production work (including set construction) had already been finished. Rodriguez just has to find a studio willing to put up the $82 million he needs.

Planet Terry:
A middle-aged scifi geek discovers he is actually an alien who has been placed on Earth as part of an intergalactic witness protection program. According to production sources it hasn't been canned yet and is still something that is in development, but couldn't say if director Brian Levant (Problem Child 2) was still attached to the project or not. The story was based on an online comic series by Rob Liefeld that has yet to premiere.

Ender's Game:
As we reported, director Wolfgang Peterson moved on to direct another Chartoff Production and Orson Scott Card is still at work crafting the adaptation of his novel into the screenplay (but the first draft is done). Filming has been pushed back to early 2009. Hurry up — I need to see my super-genius army made up of children battle it out in zero gravity. Oh, and death to all bugs.

Neuromancer:
Scripts for this film have been floating in space since 1999 but could never really find a director, Mel Gibson was once rumored to be attached to the project. In 2007 Peter Hoffman announced that he would be producing the adaptation of William Gibson's novel with a $70 million budget under director Joseph Kahn. Gibson was not pleased. In January of this year a rumor made the rounds that Hayden Christensen would be playing main character Case, but as of today no official announcement has been made. Don't you dare ruin our dark hacker Case, Hayden.

Fahrenheit 451:
Yet another scifi movie Mel Gibson tried to get his claws into. Gibson was rumored to direct the adaptation of Ray Bradbury's dystopian future novel, but now it's unclear on his position. A long list of celebrity men have been pursued for the role of Guy Montag, the book burning future fireman, including Brad Pitt, Tom Cruise and Tom Hanks (screenplay writer Frank Darabont recently stated that Hanks was no longer attached to the project.) Charlize Theron was another celeb attached to the project possibly as the free-thinking rebel Clarisse McClellan. Right now it has a release date of 2010 and no cast.

Rendezvous With Rama:
The idea to adapt the Arthur C. Clark novel has been kicked around since 2001, when Propaganda films were trying to give it wings. David Fincher (Zodiac) was announced as director this year. Morgan Freeman's production company, Revelations, owns the rights to the story and Freeman is slated as a cast member. But it's not clear yet if he will be one of the exploring spacemen checking out the sun-bound spaceship. But we hear that the draft is still getting tweaked by new writers, so it could be awhile before Rama sees the screen.

Diamond Age:
The Scifi channel announced in the beginning of 2007 a pairing with George Clooney's production company to create a scifi mini series based on Neil Stephenson's novel The Diamond Age: Or A Young Lady's Illustrated Primer. It was pitched as a 6-hour miniseries. Will we ever get to see the future of an overly conservative world, the future is uncertain.

With Reporting From Andrew Hudson