The Psychic Investigation Group (or PIG) was formed by Lizzie Corrigan in an alternate timeline as a result of the village of Stockbridge disappearing in 1950. She helped the Fifth Doctor, Nyssa and Maxwell Edison restore the original timeline in 2009, meaning that PIG was never created. (AUDIO: The Eternal Summer)
While it still existed, Lizzie told Maxwell that her PIG colleagues were fans of The X-Files and Buffy the Vampire Slayer. (AUDIO: The Eternal Summer)