Robin Hood is a supposedly famous archer and one of the few humans in Port Phasmatys, where he can be found in The Green Ghost. Robin used to be the leader of a large gang, but they eventually left him under leadership of Dirk Turnip, since Robin forced them to live in the woods and wear ridiculous outfits. The gang became a group of highwaymen, mugging people on the roads, and were dissatisfied with Dirk's callousness, but they decided to stick with him, everything being better than Robin.
If you speak to Robin before starting Ghosts Ahoy, he will brag about his fame, ask you if you have heard of him, and finally ask you to do him a favour: bring him a clean bedsheet from the innkeeper. The innkeeper is in the bar just outside Robin's room. The bedsheet the innkeeper gives you is wearable, making you look like a ghost in keeping with the Port Phasmatys theme.