Members of SCP-799 vary in size, shape, and superficial appearance, but always retain the appearance of a knit or woven item of bedding made from an unfamiliar but very soft natural fiber (resembling high-quality merino wool blend but identified as [DATA EXPUNGED]). An individual's mass ranges from approximately 0.5 to 6 kg and does not change except through ingestion and excretion, so any immediate increase in area comes at the expense of thickness and fabric "weight". The blanket retains heat unusually well. Its coloration and markings are highly variable; it tends strongly towards pastel hues and patterns resembling stylized neotenous animals, particularly when its mass is less than about 2 kg.

The items are living organisms, most similar in physiology and structure to [DATA EXPUNGED] although alternate hypotheses suggest fungal origins (full notes may be found in Document 799-1a). Although well-insulated, they are apparently cold-blooded, hence their adaptation for use by intelligent homeotherms. Instances of SCP-799 are usually torpid and incapable of movement, requiring little nutrition: what they do need, they draw from the organic detritus present in household dust. One specimen is believed to have survived for years on end stored in a damp, ill-maintained attic, living on heat from the house below and detritus from the wooden rafters above. Excretion is minimal; excreta resemble tiny, very dry [DATA EXPUNGED]. Also they can reproduce and don't eat inanimate stuff