Proteus was a very old engine from the hills of Sodor with a magical lamp. Legend has it that his lamp was magic and if any engine ever found it, their wishes would come true. The clues to finding the magic lamp are feeling a rush of wind when the lamp is near, hearing a strange creaking sound, and see a flickering light that shines on and off.
In the ninth season, Skarloey told Proteus' story to the narrow gauge engines. Peter Sam scoffed at the tale, but later realised that maybe just believing in the lamp will grant your wishes.
In the twelfth season, Miss Mary Marvel, a famous storyteller, read stories about the legend at a special show. Later, Peter Sam found a neglected statue of Proteus that was lost for many years. The statue was then restored and is now preserved in a park near the Skarloey Railway.
Proteus is painted bright yellow with red lining. All of Proteus' merchandise shows him with nameplates, even though he never had any in the television series. Proteus' TrackMaster model depicts him with gold side rods instead of his original, silver ones.
Proteus has also appeared in various magazine articles.
Proteus is likely named after Proteus, a legendary sea-god from Greek Mythology.
Proteus uses the same model as Sir Handel; however he has larger cylinders. This is because his model appears to use Peter Sam's chassis, as green edges can be seen underneath Proteus' bufferbeam and cylinder.
The statue of Proteus is missing his signature lamp.
Some TrackMaster releases of Proteus shows him carrying the number 3, like Sir Handel. This may have been a factory error of using Sir Handel's TrackMaster model with a different face and added headlamp.
His Wooden Railway and TrackMaster toys depict him with name plates despite not having any in the show.