Rumpus McFowl, also known as Uncle Rumpus, is Donald Duck's lazy uncle and Scrooge McDuck's half-brother. He was introduced by William Van Horn in It's all Relative (Walt Disney's Comics and Stories #593). Rumpus has a personality similar to Gus Goose's and his nephews have soon had enough of his manners and try to find ways to make Rumpus leave the Ducks' household.
William Van Horn said the following about the creation of Rumpus:
At the time it seemed to be a funny idea to add a new character to the duck cast, so I did it. Originally I had conceived Rumpus McFowl as a combination of W.C. Fields and Monty Woolley (from the film ‘The Man Who Came For Dinner’, 1941). A tightwad, professional cadger and notorious bum who somehow always gets the best break in the end. Once I had this picture in my head, the actual character design was easy. He just was not allowed to resemble any other duck character
Van Horn has been re-using Rumpus in his comics ever since. In his first appearance alongside Scrooge, the two were still said to be cousins.
However, in Travails (Uncle Scrooge #323), Rumpus discovers uncle Scrooge's biggest secret: Rumpus is in fact Scrooge's half-brother, and the son of Fergus McDuck. Rumpus, a lazy tramp, suddenly gets a high position in Duckburg's society after him being the half-brother of world's richest duck has become a well-known fact among Duckburg citizens.
In A Dime for Your Thoughts (Uncle Scrooge #324), Magica De Spell dates Rumpus in order to obtain Scrooge's Number One Dime.