Every brand of speculative fiction needs some kind of Other, and science fiction has aliens. If you’re including characters like this in your story, here are a few questions you must answer in your worldbuilding.

Create your aliens with care. Photo by Brian McMahon on Unsplash
Create your aliens with care. Photo by Brian McMahon on Unsplash

In science fiction, aliens and robots play the same role as dragons or elves in high fantasy. They’re the Other, monstrous or angelic, and their presence in any science fiction story indicates that reality isn’t following our rules. However, since outer space is a whole lot bigger than Middle Earth, you generally see a lot more variety in alien races than you do in otherworldly fantasy races.

While high fantasy is generally limited to elves, dwarves and other stock races from Tolkien or Lewis, the rule for aliens seems to be that if you can imagine it, they can exist. Just ask the creators of Mass Effect, Star Wars, or Star Trek.

If you’re putting any otherworldly species into your sci-fi story, there’s going to be a lot of worldbuilding involved. Here are a few ideas to get you started.

Inspiration for Alien Characters

In my posts about the fantasy genre, I’ve often said that the fantasy genre was an exercise in finding new ways to use the same old stories. But fantasy, especially high fantasy, tends to be about tradition and the past, whereas the science fiction genre is about innovation and the future. As such, you don’t always see the same recycling of tropes in every sci-fi story.

However, the section of science fiction where you find aliens tends to be more fiction than science, so there’s still a sharing of ideas throughout the genre. If you’re putting aliens in your sci-fi story, I’ll use the same advice I used for fantasy writers: look at the classics.

For the science fiction genre as a whole, I’d say that some of the best examples of alien worldbuilding are the TV show Babylon 5 (which takes place on a space station, a sort of interstellar United Nations) and the video game series Mass Effect (which has a wonderfully complicated cast of characters and about two dozen named alien species).

On the literature side, Ursula K Leguin has several wonderful books centered around alien species, ranging from lunar wars of independence to comedies of manners involving four-person marriages. If you’re trying to figure out what a truly alien society might look like, Leguin may be worth a read.

What’s Their Home Planet Like, and How Did It Shape Them?

An alien's home planet should be as varied as they are. Photo by Daniel Olah on Unsplash
An alien’s home planet should be as varied as they are. Photo by Daniel Olah on Unsplash

An important factor for worldbuilding is what the home planet looks like for your species. As a general rule, all organisms are influenced by their environment.

If you have a generally humanoid species, your planet will probably look something like Earth. Even within those bounds, there’s likely to be strong connections between your species’ character, culture and appearance, and the environment they developed in.

If you’re stuck trying to figure out how this might happen, try to find a biome or region of Earth that resembles your species’ planet. Check out the plant and animal life of that region, or even the cultures that developed there. Obviously your planet won’t have the same wildlife or the same people, but it might make sense to have some similarities.

If, on the other hand, you’re going for some kind of deep-space weirdness for your alien species, you might want to create a planet that’s deadly enough to justify it. You could even try looking up other planets in our solar system, or some of Planet Earth’s more extreme biomes, to give you some scientific ground to stand on. If you’ve ever seen a picture of the bottom of the ocean or the freaks of nature who live there, you’ll know what I’m talking about.

How Sympathetic Do You Want to Make Your Aliens?

Most writers will tell you that sympathy comes from similarity. The more human your characters seem, and the more like our culture their culture seems, the easier it will be to portray them as a benevolent race who might become allies with humanity. The more different from humanity they are, the easier it will be to get away with portraying them as monsters.

Of course, there are exceptions to every rule, and some of the best alien stories out there are exceptions to this one. Ursula K Leguin’s aliens tend to be human-shaped, but their societies tend to treat the taboo as normal. The results were pretty fascinating. “Solitude” is the testimony of a woman in a society based entirely on extreme introversion. “Mountain Ways,” from the same collection, is a romantic comedy involving a four-person marriage.

Likewise, the movie District Nine took the “similarity equals sympathy” rule and used it to explore human prejudice. The aliens who landed in District Nine’s South Africa are, physically speaking, not that different from the monsters in War Between the Worlds. But in this story, they’re not invaders but refugees – and the way most humans react to them is chillingly reminiscent of real-life racism and nationalism.


In soft science fiction, aliens play the same role that dragons or elves play in fantasy, or that mysterious foreign operatives play in spy fiction. They’re the Other, the exotic, pushing the bounds of what we call normal. How you decide to use that in your story in up to you.