The Guardian of the Gates
The Guardian of the Gates was the man who manned the great entrance gate of the Emerald City of the Land of Oz in many versions of Oz.
In one universe whose Oz was visited by Acquaintanceship-982, he appeared as a short, elderly man whose skin was slightly greenish. This was accented by his clothes, all in shades of emerald green, and the green-tinted goggles he wore at all times. Even years after the Wizard of Oz was deposed, he continued guarding the gates and asking visitors to put on goggles before entering the City, now genuinely to guard themselves against its great brightness rather than as a scam. Acquaintanceship encountered him when he first headed into the City, convincing him that as a clockwork being, his eyes had nothing to fear and he did not need additional protection. (PROSE: The Crew of the Copper-Colored Cupids in Oz)
Behind the scenes
The Guardian of the Gates debuted in the original 1900 Wonderful Wizard of Oz novel, meaning he is in the public domain. His species was never clarified in Baum's books, with his Munchkin-like proportion and greenish skin presumably marking him out as non-human.