Floof

Floofs were short humanoids with the super-evolved ability to hide.

Biology
Floofs resembled short humanoids, commonly with bald heads. Over time, they evolved to become experts in hiding. This allowed them to find the one spot that no-one was looking at in a room full of people, which would keep them out of sight from people. They generally stalked humans or other humanoids, causing mischief in the person's life. However, sometimes the Floof became possessive and began to cause more serious problems. They probably had superhuman speed, as they could travel to places where no-one could see them extremely quickly. (DWS: Corner of the Eye)

History
One Floof lived in England in the 21st century in the house of a man called Tom. The Floof, who had become addicted to causing mischief in Tom's life, killed his wife Kathy. In fear of being discovered, he hid the body in the basement and manipulated Tom into thinking that he and his wife lived separately and spoke over online messaging, despite the fact that Tom did not have an internet connection. The Doctor arrived at Tom's house, telling him about what had happened to Tom and summoning the Floof from its hiding place. The Doctor also discovered Kathy's body in the basement. He made Tom realise what had happened, and Tom agreed to leave the house, abandoning the Floof. However, he agreed to leave an artificial version of himself on his personal computer, which would talk to Kathy's AI on a regular basis, keeping her company forever. (DWS: Corner of the Eye)