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. (COMIC: Doctor Who and the Iron Legion)

History
On an alternate Earth ruled by the Roman Empire, Ectoslime were used in fights in the Hyp-Arena. They were very popular with the crowds, with their own admirers known as "Eccy fans". The Fourth Doctor knew the Ectoslime before and had them in his memory files. He was thrown to one, but he avoided death by telling it a joke in an alien tongue. When brought before General Ironicus afterwards, the Doctor attempted to translate the joke for the robot regent ("These three aliens walk into a bar, and the first alien says..."), but Ironicus ordered the Time Lord to be silent as the purple light on his chestplate — which permitted others to speak to him — was not illuminated at the time. (COMIC: Doctor Who and the Iron Legion)