Type 1

The  TARDIS design was an early prototype created by the elders of ancient Gallifrey. It was poorly designed, dangerous and hard to start. Some of them had minds of their own, with a history of escaping and roaming the Universe.

The Second Doctor discovered an old, decrepit woprat on a TARDIS in an Avatar universe. Jamie killed it before the Doctor could get a closer look. (PDA: Heart of TARDIS)