Kera-Bera Beast
From Tardis Wiki, the free Doctor Who reference
Kera-Bera Beasts were purple, parasitic creatures which created an illusion to become close to an individual. They 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. (DWA: The Stray)
