When Doctor Who returned to television screens in 2005, fans got to meet a new Doctor and a new companion. Christopher Eccleston had taken over the TARDIS as the Ninth Doctor and Billie Piper was by his side as new companion Rose Tyler. Rose would go on to become hugely significant to the Doctor, traveling with both the Ninth and Tenth Doctors across the revival's first two seasons. She later returned in Season 4 and would factor into the events of the 50th Anniversary special, "The Day of the Doctor."
Source：https://www.cbr.com/doctor-who-bad-wolf-references-explained/
