Catherine Broome

Catherine Broom - or Cat - was an android built by the Seventh Doctor. She was unaware that she was an android and believed herself to be a twenty-eight year old human female from the late 20th century. (PROSE: Companion Piece)

Biography
Cat was build by the Seventh Doctor because he was tired of travelling alone and all his invitations had been declined. She thought she was from the 20th century because many companions did come from that time. At some point she faced the Cybermen alongside the Doctor. (PROSE: Companion Piece)