Group Marshal Cat was a cat taken in by Major Kreg shortly after arriving at Mumbles Bay Caravan Park, having decided that the prolificity of cats on the Internet meant that they were worthy of study.
Living in Kreg's caravan, Group Marshal Cat had a habit of sitting on the keyboard of Kreg's laptop, which Kreg believed was his attempt to keep him from getting too close to "the truth". Ianto Jones tried to have Toshiko Sato take Group Marshal Cat in despite her serious allergy, but he ultimately remained at the caravan park. (AUDIO: The Great Sontaran War)