Throughout film and television, science-fiction writers and visionaries have struggled to portray intelligent extraterrestrial life. Having not yet seen any, we simply cannot envision what it would look like.

We may guess, dream and fantasize, but in actuality, we have no idea how non-humanoids would appear. So this column will illustrate several classic examples of extraterrestrials (a.k.a. aliens) and whether they lived up to our expectations.

Of all of the shows currently on television, only five actually depict alien life: V, Stargate: Universe, Doctor Who, Torchwood and Smallville. While V and Smallville are limited to depictions of a single non-human species (the reptilian Visitors and Kryptonians), Universe, Doctor Who and Torchwood cover a larger array of alien lifeforms. (It is debatable whether any true alien life has been portrayed on Caprica yet, which mostly consists of humans inhabiting other planets and man-made machines and computer-generated avatars.)

Then, of the 2009 theatrical films, only Avatar, District 9, Transformers: Revenge of the Fallen, Star Trek, Race to Witch Mountain and Outlander depicted non-terrestrial life forms. (Not including animated films.) Avatar had the Navi; District 9 had the Prawns; Transformers had alien robots; Star Trek prominently featured Vulcans and Romuluans; Race to Witch Mountain had a couple of kids from an unidentified planet; and Outlander had the monstrous Morween.

Looking at just these most recent examples, it is hard to say how we truly view extraterrestrial life. We clearly have not seen it yet and, as a result, our imaginations have run away with the unlimited possibilities.

To help distinguish the categories we have come up with to depict alien life, here is a list:

* Humanoid (Catpeople, Ewoks, Klingons, Kryptonians, Ood, Navi, Predators, Sontarans, Time Lords, Weevils, Wraith and Wookies);

* Insectoid/arachnid (Bugs like in Starship Troopers, Prawns like in District 9);

* Reptilian/amphibian/aquatic (Draconians, Judoon, Predators, Slitheen, Silurians);

* Parasites/symbiots (xenomorph like in Aliens and black oil like in The X-Files);

* Robotic/mechanical (Borg, Cybermen, Cylon, Daleks, Replicators, Transformers);

* Rodent (Tribbles); and ancient/primordial (the Ancients like in Stargate).

Looking back at the most influential sci-fi films of the past 40 years, the most glaring examples of alien encounters have been in: 2001: A Space Odyssey, The Abyss, Alien, Avatar, Close Encounters of the Third Kind, Invasion of the Body Snatchers, Contact, District 9, E.T., War of the Worlds, The Day The Earth Stood Still, Independence Day, Men In Black, Predator, Species, Star Trek, Star Wars, Stargate, Starship Troopers, Superman, and Transformers. This is not a comprehensive list, but these are the most easily recalled films that shaped our perception of how alien lifeforms would appear.

It is notable that several of these films simply chose to not show what aliens would look like, such as 2001: A Space Odyssey, The Abyss, Close Encounters of the Third Kind, Contact, The Day The Earth Stood Still, Star Trek, Stargate, Superman. Instead, we only saw aliens appearing in human form or not shown at all. Utilizing this method of appearance tends to feel more realistic to viewers as we feel more comfortable being addressed or greeted by alien life in a familiar body or form.

Therefore, it is interesting that several other key sci-fi films actually chose to create alien races, such as: Alien, Avatar, Invasion of the Body Snatchers, District 9, E.T., War of the Worlds, Independence Day, Men In Black, Predator, Species, Star Wars, Starship Troopers, and Transformers. These films did not wish to be constrained by the expectation of aliens looking just like us. They wanted to stretch the fabric of storytelling and paint a picture of new lifeforms - alien life from somewhere beyond Earth.

In Alien, we were introduced to parasitic alien life, the kind that can inhabit a human host during gestation, which were subsequently reintroduced in Invasion of the Body Snatchers and Species. In Avatar, there was the Navi, the 10-foot tall blue people. District 9 introduced the Prawns, insectoid aliens. E.T. portrayed the lovable little extraterrestrial befriended by a boy.

In War of the Worlds, there were the gigantic robots inhabited by tiny aliens. Independence Day had alien creatures similar to those portrayed in Predator. Men In Black had all kinds of bizarre alien life. Star Wars had a vast array of aliens including Wookies and Ewoks. Starship Troopers had bugs. And Transformers had alien robots.

All in all, filmmakers and television creators have taken delight and liberty in envisioning what non-Earthlings would look like. For the most part, we as the audience sitting in a movie theater or watching a television show are open-minded to all the possibilities and artistic license. Particularly for those fully immersed in the sci-fi realm who are used to the parade of aliens throughout epic films and television series such as Star Wars, Star Trek, Doctor Who and Torchwood.

Because sci-fi fans also are very accepting of the idea that not everyone feels comfortable trying to portray something not yet seen and that aliens may come to us in human appearance, we forgive the lazy or hesitant filmmaker. But are sci-fi fans as forgiving and understanding to filmmakers who dare to unveil their idea of what alien life looks like? From my own perspective, sci-fi fans are tolerant, but not always understanding.

One glaring example from television was the short-lived series Defying Gravity. I know I was extremely surprised when they finally revealed the entity known as Beta, as well as a bit shocked. The name alone should have been an indicator of what to expect, but in hindsight it was rather startling to find out that Beta was a square glowing cube approximately the size of a football, which looked more like a futuristic version of a Rubiks cube than a form of advanced alien life.

It was a clever idea that, in the entirety of the universe advanced beings, alien life could be made up of pure fractals. But, it sure made it hard to relate to when watching it on the television screen. It resembled an advanced computer more than an alien lifeform. It also was eerily reminiscent of Battlestar Galacticas Cylon technology, which had ultimately evolved from integration of human cells surrounding Cylon computer interface.

Was Beta truly anything like an alien, or was it more computer-like?

So this led to the analysis of whether our expectation of what aliens should look like is reasonable: Should aliens appear in humanoid form, creature form or parasite form? Should alien life be confined to a body at all? Could it be more of an unseen collective consciousness?

In reality, alien life could be all of these things - we simply do not know yet. But as far as portrayals in film and television, is it alienating to portray aliens so simplistically as a glowing cube?

When pulling back the curtain we have heightened expectations that aliens will be more intriguing and interesting than anything we have seen before. As a sci-fi fan, I love discovering new life and all its wondrous possibilities. When the first alien jumped out of the chest in Alien, I screamed with equal parts horror and delight. It was both disgusting and fascinating.

Then in Aliens when we saw the mother alien, my blood ran colder. It was bone-chillingly awesome. Perhaps no other alien incarnation in film and television has been so persuasively foreign to everything we know and perhaps want to know. Even the Predator could not invoke such awe.

Seeing the Prawns of District 9, while not as purely evil in appearance, still brought the wonder of what intelligent, foreign extraterrestrial life will look like when encountered.

Will sci-fi aliens of our future be humanoid like depicted in Avatar, insect-like like in District 9, or will they actually be more fractal-like as shown in Defying Gravity? Without actually encountering extraterrestrial life and seeing for ourselves, it remains perplexing and challenging to envision it. Let us all hope that one day, if and when we do have such an alien encounter, that it lives up to our heightened expectations.