Puss was a cat.
In 2007, when ghosts began to appear all over the world, Suzy Monroe was filming them for Ghostwatch. She took a look at some viewers' sightings and found a cat, which she called Puss. Suzy was relieved that the cat wasn't a ghost and talked to the cat. Then Suzy left to take a look at some other viewers' sightings and was attacked by a Cyberman.(WC: Ghostwatch)