Nuppino horse
From Tardis Wiki, the free Doctor Who reference
Nuppino horses were large animals with purple skin, and darker purple spots.
One individual was locked up on the planet Refkeet Nine. Its captors intended to use the creature to "teach the Doctor a lesson", and sent a psychic message which accidentally invited both the First and Eleventh Doctors. The Eleventh Doctor released the Nuppino horse, asking it to give its captors a "little scare" as it ran off. (COMIC: Time Trick)