- Human Aliens
- Human Subspecies
- Not Quite Human
- Rubber Forehead Aliens
- Humanoid Aliens
- Petting Zoo People (sometimes they're aliens)
- Little Green Men
- The Greys
- The Reptilians
- Little Green Man in a Can
- Insectoid Aliens
- Intelligent Gerbil
- Mechanical Lifeforms
- Alien Animals
- Blob Monster (amoeba)
- Killer Space Monkey
- Space Whale
- Sand Worm (worms)
- Big Creepy-Crawlies
- Low Culture, High Tech
- Plant Aliens
- Starfish Aliens
- Silicon-Based Life
- Energy Beings
- Genius Loci
- Sufficiently Advanced Alien