He is described as being made of dark matter. He, along with many of his kind, was used as a slave on board a galley by a group of pink humanoids, untill he escaped to earth, where he ended up in Toyland. There he met Frankenstein's Monster, who provided him with two companions: the Dutch Dolls.
Now, the Galley-Wag is the owner of a ship called the Rose of Nowhere, a balloon-type craft that uses pataphysical rose-propulsion which allows it to cross dimensions and the void of space. He is also an acquaintance of Prospero.
He plays a prominent role in The League of Extraordinary Gentlemen: Black Dossier, in which he rescues Mina and Allan and takes them to the Blazing World. He also plays a part in Minions of the Moon, in which he, his dolls and Mina are send on a mission to the Moon by Prospero to avoid a war between the Selenites and the Lunites.
The Galley-Wag is capable of emitting a loud screaming noise that can apparently shake the earth and knock down anyone who hears it. He uses this to hold off Jimmy Bond, Emma Night and Hugo Drummond in The Black Dossier. His text balloons in the comic are colored black, possibly to indicate he has a deep, alien voice.
The Galley-Wag is based on a black character in children's books in the late 19th century, depicted as a type of rag doll. The image of the doll has become the subject of heated debate since it is considered to be a racial stereotype of African Americans. To avoid any controversy about the character, Alan Moore reimagined the Golliwog as an alien for his comic book series.