Aunt Fanny's letter.

Fanny the Goose (born Fanny Coot) is the mother of Donald Duck's cousin Gus Goose. She was first mentioned in the Donald Duck comic strip of May 9, 1938 by Bob Karp and Al Taliaferro, where Gus first appeared. This comic was an adaptation of the animated short Donald's Cousin Gus, which Gus' mother was also mentioned. Her surname wasn't revealed in both media, where she identifies herself in a letter to Donald as Aunt Fanny, implying that she was originally meant to be a sister of one of Donald's parents. When Carl Barks created his Duck family tree for personal use in the 1950s, he included Gus as a nephew of Luke the Goose, making him a distant "cousin" of Donald's. In Mark Worden's illustrated version of Barks' first tree, Gus' unnamed mother appeared on a portrait.

However, when Carl Barks drew a new tree in the 1990s, he included Fanny as Grandma Duck's daughter and Donald's father Quackmore Duck's sister.

In Don Rosa's 1993 Duck Family Tree, she is featured as a daughter of Casey Coot and his wife Gretchen Grebe, and therefore a niece of Grandma Duck, and first cousin of Donald's father. According to this same tree, Fanny married Luke the Goose, and then became the mother of Gus Goose. On this tree, Fanny was placed as the sister of Cuthbert Coot, Donald's cousin from the Carl Barks comic Donald Learns the Ropes.

Aunt Fanny and her husband made a brief cameo appearance in Dangerous Currency (2011).