Build an Alien

There are a bunch of basic approaches to creating aliens, whether they are intended to be PCS, NPCs, or just critters: Bumpy Forehead, Calling A Rabbit a Smeerp, Bespoke Aliens, Bug-Eyed Monsters, Swiping.

Bumpy Forehead Aliens

If you’ve seen any SF television at all, you’ve seen these guys.  They’re humans, painted a different color and maybe with a few prosthetic enhancements: a wrinkly rubber forehead, a pair of antennae, pointy ears.  It’s cheap, it’s convenient, and in terms of story-telling or gaming it’s super useful. You can’t overstate the importance of things like being able to read an alien’s expression and body language, being able to disguise yourself as an alien or vice-versa, or even the possibility of cross-species romantic entanglement.  Unless you carefully remind the players in every interaction they have with a particular alien just what it looks and acts like, and deliberately make it weird and memorable, this is pretty much the mental image players are going to have of 90% of the aliens they encounter.  My recommendation is that you embrace it rather than fight it.  Even though in one sense an RPG gives you an unlimited special effects and make-up budget to work with, in another very real way you are even more constrained than a weekly TV series, where at least once you’ve got the alien in costume/added the CGI effects the viewers have the image constantly before them. Conveying what’s going on to the players is a lot easier if you can simply say “the blue alien”, “the alien with the horn in its forehead”, “the four-armed alien” at least after a more elaborate introduction.  If you have very few types of aliens in your campaign, you can probably afford to put more effort into making them unusual and truly distinct from each other but if you want something more like the StarWars cantina, or even Star Trek, you’re going to need at least some of them to be easy to describe and imagine filler.

Predominant Color of Alien

Use a d6 for quick, basic colors, a d8 for a wider range, and a d12 to include exotic possibilities.

  1. Red
  2. Orange
  3. Yellow
  4. Blue
  5. Green
  6. Indigo
  7. Violet
  8. Multi-color (reroll for which)
    1. Stripe
    2. Spot
    3. Half-n-half
    4. Gradient
    5. Highlights
    6. Geometric pattern
  9. Transparent
  10. Sparkling
  11. Glow-in-the-dark
  12. Radiant

Unusual Features

Roll a d6 through d12, depending on how unusual.

  1. antennae
  2. horns
  3. fangs
  4. feathers
  5. scales
  6. spikes
  7. pits/holes
  8. ridges
  9. fins
  10. patches of fur/hair
  11. tentacles
  12. Exotic
    1. sparks
    2. flames
    3. miasma
    4. glowing light
    5. Kirby dots
    6. changes from one to another (reroll d12)

Location of Feature

Roll a d6 through a d20 depending on how unusual

  1. Temples
  2. Brow
  3. Cheeks
  4. Ears
  5. Neck
  6. Chin
  7. Crown of head
  8. Back of Head
  9. Shoulders
  10. Elbows
  11. Spine
  12. Waist
  13. Hips
  14. Forearms
  15. Fingertips
  16. Knees
  17. Thighs
  18. Shins
  19. Feet
  20. Multiple (reroll)

Calling A Rabbit A Smeerp Aliens

Even if the aliens aren’t basically humans with makeup, it’s a staple of SF to describe aliens in terms of their similarity to terrestrial animals, or combinations thereof.  Face it, if people describe clouds, rock formations, and animals themselves in terms of their resemblance to animals they’re not going to be able to resist doing so for alien species.  Technically, calling a rabbit a smeerp is when you try to disguise just how the prosaic the alien is by giving it a funny name, but here I’m using it to describe every sort of “It looked a bit like a bipedal wolf, but covered with tiny scales” alien.  You can combine the handy chart below of just what the alien appears to be a cross between with the charts above for color, special features, or perhaps which locations on the alien resemble which animals.

Naturally, the results are just reminiscent of those kind of creatures to humans familiar with Earth animals (the players). Just because your alien is bat-like doesn’t mean that it has to have leathery wings and use echolocation and be mammalian, nor do your bird-like aliens have to have feathers and wings and lay eggs (although that’s certainly how some SF writers like Rebecca Ore have done it).


Roll 1d4 for how many animals to mix: 1 = 1, 2-3 = 2, 4 = 1 + reroll .  Roll  from 1d4 to 1d100 for type(s) depending on how specific you want to get (smaller dice give you broader categories).  If using larger than a d4, you should probably add 4 to skip the largest categories.

  1. animal
  2. vegetable
  3. fungi
  4. exotic
  5. mammal
  6. reptile
  7. bird
  8. fish
  9. insect
  10. invertebrate
  11. amphibian
  12. slime
  13. mineral
  14. energy
  15. dog
  16. cat
  17. bear
  18. bee
  19. cow
  20. monkey
  21. dinosaur
  22. worm
  23. starfish
  24. jellyfish
  25. sponge
  26. mushroom
  27. tree
  28. spider
  29. beetle
  30. frog
  31. crustacean
  32. aardvark
  33. alligator
  34. antelope
  35. badger
  36. bat
  37. bear
  38. beaver
  39. bison
  40. boar
  41. camel
  42. canary
  43. centipede
  44. chameleon
  45. cheetah
  46. chipmunk
  47. cow
  48. coyote
  49. crow
  50. deer
  51. donkey
  52. eagle
  53. elephant
  54. ferret
  55. finch
  56. fox
  57. frog
  58. gila
  59. giraffe
  60. gnu
  61. goat
  62. gorilla
  63. hare
  64. heron
  65. hippopotamus
  66. horse
  67. iguana
  68. jackal
  69. jaguar
  70. kangaroo
  71. koala
  72. leech
  73. lion
  74. llama
  75. mole
  76. mongoose
  77. moose
  78. newt
  79. opossum
  80. otter
  81. panda
  82. parrot
  83. pig
  84. porcupine
  85. praying mantis
  86. raccoon
  87. rat
  88. rhinoceros
  89. seal
  90. sheep
  91. skunk
  92. sloth
  93. snake
  94. squirrel
  95. tiger
  96. turtle
  97. wasp
  98. wolf
  99. wolverine
  100. woodchuck
  101. worm
  102. mineral
  103. energy
  104. shape-shifter

Bespoke Aliens

Meaning an alien that is made-to-order to seem as scientifically plausible as you know how to fit in with an imagined extraterrestrial locale and ecosystem.  Care is usually taken to make it seem different, perhaps radically so, from terrestrial examples.  Often it’s designed in such a way as to provide a puzzle to solve, e.g. in the Star Trek episode The Devil In The Dark, the explanation of the alien monster’s hostile behavior is that it was trying to protect the silicon nodules the miners didn’t recognize as being its eggs since they weren’t thinking in terms of silicon-based life.

With a bespoke alien, some thought will be given to its life-cycle, its ecological niche, and things like its modes of reproduction, respiration, nutrition, transport, excretion, growth, etc.  While it’s not really practical to roll everything up randomly, you could use the Baseline chart above to suggest the ecological niche or certain of its biological strategies based on terrestrial animals. E.g. a roll of tiger could indicate that it’s a solitary apex predator, or perhaps that it uses camouflage, or perhaps just that it’s about the size of a tiger.  Wikipedia can be a real help here, letting you pick an choose interesting facts about a creature’s biology you can swipe for your alien.

  1. Predator
  2. Herbivore
  3. Omnivore
  4. Scavenger
  5. Parasite
  6. Symbiont

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