Dog

Leaky, a domesticated dog. (DW: Image of the Fendahl)

Meow.

Other information

• K9 was made in the form of a dog, but was given advanced technology and human-level intelligence. (DW: The Invisible Enemy)
• A type of dog is found on Barcelona. The only known difference between them and Earth dogs is their lack of noses. (The standard joke, which the Ninth Doctor references, is "But how do they smell?"--to which the answer is "Terrible!") (DW: The Parting of the Ways)
• Rose was a small female dog that belonged to Jackie and Pete Tyler in an alternate version of Earth, referred to as "Pete's World" by the Tenth Doctor. Rose represented the alternate version of Rose Tyler - the daughter of Jackie and the deceased Pete Tyler in the Doctor's native universe. (DW: Rise of the Cybermen)
• The dog Teazel was captured by Zygons and the warlod Brelarn used his Body Print, as dogs can go where they like. (NSA: Sting of the Zygons)
• The Cybus Cybermen converted dogs into two types of Cybernetic servants, Cyberdogs and Cybershades. (DWBIT: Enemy Mine, DW: The Next Doctor)
• Prisoner Zero took the form of Barney Collins and his Rottweiler. This was because the real Barney Collins, in a coma, was dreaming about walking his dog. (DW: The Eleventh Hour)