Kelgians are roughly human-sized, resembling fat, cylindrical caterpillars with long, thick, silver fur. Their bodies do not possess a skeleton, except for a narrow, conical head casing and delicate spine; broad circular bands of soft muscle tissue provide protection as well as helping them move. They have 12 pairs of stubby legs with feet like small, hard sponges, lacking toenails or any other hard parts, and walk slowly with a wheeling, undulating gait. They also have four pairs of thinner, longer (but still short) arms with tiny, delicate, pink triple-fingered hands. They have tiny, tightly grouped facial features -- two hearing antennae, four eyes on extensible stalks and two mouths (one for speaking, one for eating).
Their environmental requirements (land-based, 1G, oxy-nitrogen atmosphere at standard pressure) are fully compatible with humans. They are herbivorous, eating shredded greenery (such as crelletin vine shoots) by burying their heads in the bowl. They can stand on their rearmost four legs in a question-mark pose with faces at human eye level and sleep in an S shape (in zero gravity or on beds).
The Kelgian circulatory system is complex and vulnerable, with two hearts and many fine vessels near the surface. This, combined with high pressure and a high pulse rate, makes cuts very dangerous; a Kelgian can bleed to death from a minor injury if not tended. Their skin is thicker than an Earth-human's.
Their most noticeable physical feature is their fur. This silvery covering is permanently in motion, eloquently expressing their feelings (to another Kelgian). It is sparse at the neck and bushy on the upturned tail, and Kelgians with rank usually dye their fur with insignia rather than covering it with a uniform. If fur is removed it will never grow back properly, reducing the victim's appearance; this is very distressing, and doctors will shave as little as possible when operating.
Because their feelings are always obvious to others, Kelgians never developed the concepts of tact or lying, and are never shy. They are always forthright in their views and will not hesitate to criticise superiors if they believe a mistake has been made. This can be disconcerting for those not used to dealing with them (and occasionally annoying even to those who are).
To a human being, their speech sounds like hoots and whines. Females only conceive once in their lives, producing two children of each gender.