Goblin

Goblins were a species of short, green-skinned humanoids with prominent noses and pointy ears. They had a place in human folklore, and the term was sometimes used in general terms to refer to a magical trickster, rather than to a specific trickster; in this figurative sense, the Doctor was sometimes compared to a "goblin".

History
Goblins, among other creatures, were present on a battlefield in the Slough of the Disunited Planets. The Tenth Doctor, Alistair Gordon Lethbridge-Stewart and Michael Yates comforted one mortally wounded goblin as he died. (COMIC: The Warkeeper's Crown)

Goblins also had a place in human culture and folklore. One of the props stored in an old pantomime theatre prop-room was a goblin costume; after Thirteenth Doctor attempted to summon the "magic of pantomime" to life using a link she'd clicked on Spacebook, it turned out to be very literal, replacing the props with real versions of the various characters, "snatched" from their homes against their will. This included a sword-wielding goblin. Before long, however, the Doctor found and rubbed the now-real magic lamp and summoned a Genie, using the first of her three wishes to get him to send away all the other, more dangerous fictional beings the Spacebook link had summoned. (COMIC: It's Behind You!)

As fantastical creatures in human folklore, goblins were brought into existence on Avalon by the nanobot system on the planet, which realised the fantasies of 22nd century human colonists. As such, goblins had an entry into the Avalonian Bestiary. Also in the book were bogies, which were described as shape-shifting goblins. (PROSE: The Sorcerer's Apprentice)