Tin Fish are an alien species which live on an asteroid in the Other Solar System. They are flat, round and about 30 to 35 cm in diameter at full size. They are tin based organisms, unlike the carbon based life which is common on Otherworld. Their asteroid is usually simply called the "Tin Fish Rock" or "Tin Fish Base". Tin Fish are intelligent, sentient creatures, but their way of thinking is very different to that of other species. They communicate with each other by sending out radio waves which other Tin Fish can pick up with antennae on their heads.
Tin Fish have their own language and names for their species and home asteroid, but it is difficult or impossible to pronounce for a human. Tin Fish are able to survive in complete vacuum, can withstand extremely high doses of radiation, and extreme temperatures, hot or cold. However they are by no means invincible, and can be killed by heavy impacts, such as being stomped on. In outer space they are quite mobile, but on the surface of worlds with high gravity they are only able to flop and slither about. Despite this weakness, they have grand plans to conquer Otherworld and enslave its inhabitants as a giant mining colony. Tin Fish are skilled at making metal objects, which they achieve by some type of metalkinesis power.
Almost everything they make is a characteristic silvery grey colour. They are considered a joke, and none of their attempts to conquer any part of Otherworld have so far been successful. Nonetheless, they are determined and never give up their attempts. The Tin Fish emotional spectrum is quite different to that of terrestrial animals and peoples as well. They have no concept of certain emotions common to humans, but they have other emotions which are difficult to describe or understand.