The Crewmates are a species of aliens from an unknown planet.
While not much is known about their biology, they have the appearance of squat humans in space suits. For whatever reason, they have a single femur bone where the spine should be. They also breathe oxygen, suggesting their planet has the atmosphere as Earth.
The only known aspect of their culture is their use of technology. Though they also keep pets such as smaller version of themselves, and they also appear to have domesticated headcrabs, specifically a variant called a "bedcrab". Other pets include dogs, squigs, and brain slugs. They also refer to each other by their colors.