Kera-Bera Beast

Kera-Bera Beasts were purple parasitic creatures that created an illusion in order to become close to an individual. They then fed off that individual before moving on to another. One Kera-Bera Beast which became stranded on Earth was 'adopted' by Betty, who (through an illusion) believed it to be a Yorkshire Terrier. The Eleventh Doctor and Amy Pond intervened and, with a bit of planning, broke the psychic link. They used a hairdryer at Betty's hairdressers to restore Betty’s energy and to persuade the Kera-Bera Beast it was actually a cute dog. Betty continued to care for it and keep it for company. (DWAM: The Stray)