The Proteus system was named after this character.
In 2366, Deanna Troi had a waking dream in which Proteus and a band of Other-worlders assaulted CephCom, the headquarters of Cephalic Security in the city of Verity on the planet Rampart. In front of her, Proteus shape-changed from a human into a fish, a puddle, and then into the mythological Cerberus, the three-headed dog, frightening the security officers. Following the assault, as Other-worlders were helping an officer out from under a jeep, Proteus took the shape of a stretcher to help the officer. (TNG novel: Gulliver's Fugitives)