Ectoslime

Ectoslime were giant, slug-like creatures.

Biology
Ectoslime stunned their prey with their odour before liquefying and drinking them. They communicated verbally and had a highly developed sense of humour to compensate for their appearance. (DWM: The Iron Legion)

History
On an alternate Earth ruled by the Roman Empire, Ectoslime were used in fights in the Rome Hyp-Arena. They were very popular with the crowds, with their own admirers known as "Eccy fans". The Doctor was thrown to one, but he avoided death by telling it a joke. (DWM: The Iron Legion)


 * Since the Doctor had already heard of Ectoslime, it would seem that they exist in his own universe as well.