Scrooge's father was originally created by Carl Barks, who mentioned him in his 1950s Duck Family Tree. Barks gave Scrooge's father the name Old 'Scotty' McDuck.
The first time Scrooge's father was mentioned in a comic book was in A Tree For Free (1962), drawn by Tony Strobl and first published in the first issue of Walt Disney's Christmas Parade. In this story, we learn that Scrooge's father owned a trading company called 'Duck & McDuck', together with Daisy Duck's great-great-grandfather.
In the 1977 Uncle Scrooge comic Zio Paperone e l'oro del Klondike ("Uncle Scrooge and the Gold of the Klondike"), drawn by Romano Scarpa, Scrooge's parents made their very first appearance. In this story, Scrooge's father, referred to as Paperon-Papà in the original version, is a local shopkeeper who sells prospector equipment in the Klondike. In the story, he and Scrooge's mother, called Oretta Paporetta in Italian, have been dating for years, but did not get married, because both of them were too stingy to pay the local marriage fee of 1 dollar. Eventually, Scrooge's mother decides to pay the fee and the two ducks marry at last. The story also covers the birth of Scrooge McDuck and the first meeting between Rockerduck's parents.
In 1981, Mark Worden made an illustrated version of Carl Barks' 1950s Duck Family Tree, in which all relatives were given their own portrait. On this tree, Old 'Scotty' McDuck had a beard and wore a Scottish beret.
Scrooge briefly mentioned his parents in the DuckTales episode "The Curse of Castle McDuck". When Scrooge returns to his childhood home, cottage McDuck, he reveals that his parents were poor, simple farmers.
Scrooge's parents made their animated debut in the season 1 episode "Once Upon a Dime", in which Scrooge refers to Fergus as 'McPapa'. In this episode, it's told that Scrooge and his father both played the bagipes. McPapa, Scrooge and Scrooge's mother could be seen living in cottage McDuck, as it previously appeared in the series. McPapa was guest voiced by Don Messick, who gave him a thick Scottish accent.
In the NES game DuckTales 2, Scrooge and his nephews find a piece of a treasure map that once belonged to Fergus. It claimed to lead to Fergus' lost treasure.
Fergus' name origins from the The Life and Times of Scrooge McDuck, in which he was a prominent character. In these stories, Fergus lives in Glasgow with his wife and children. The family is very poor in these stories, implying that Fergus somehow lost his fortune. He encourages his son to work in order to earn his own money. Scrooge's obvious intelligence, skill at hard work and ambition make Fergus believe that Scrooge will be able to restore The Clan McDuck to its former glory.
In The New Laird of Castle McDuck (Uncle Scrooge #289), young Scrooge returns to his family in Scotland, because there is a threat of the Clan's hereditary lands being seized due to Fergus' inability to pay the taxes. Using all of the money he has earned so far, 10,000 dollars, Scrooge is able to pay the taxes and becomes the new owner of their lands.
After years of hard work, Scrooge becomes rich in the Klondike and returns to Scotland as a billionaire, as shown in The Billionaire of Dismal Downs (Uncle Scrooge #293). Scrooge's original intention to settle in Dismal Downs quickly changes and Scrooge decides to move to Duckburg. Scrooge's sisters go with him, but Fergus decides to stay in Scotland.
According to William Van Horn's Travails (Uncle Scrooge #323), Fergus at some point had a short marriage with an unidentified woman, with whom he had one son: Rumpus McFowl. He later married Downy O'Drake, his wife in further stories, who became the mother of Scrooge and his sisters Matilda McDuck, and Hortense McDuck, whose names also origin from the Duck family tree sketches Barks did in the 1950s. Given the fact that Scrooge has a full brother called Gideon McDuck, Fergus and Downy must have had at least one other son.
In A Letter from Home (Uncle Scrooge #342), it's revealed that Fergus tried to find the Knight Templar treasure hidden in the castle McDuck by one of his ancestors, a Knight himself. Even though Fergus decided not to tell Scrooge about the treasure, the latter learns about it through other ways and, like his sister Matilda, thinks Fergus kept the secret from him because he disapproved Scrooge. In the middle of their way to the treasure Matilda finds a letter from Fergus revealing the reason he hid the secret from Scrooge is that Scrooge would feel better building his own fortune instead of inheriting one.
Fergus reappeared in Scrooge's flashback in the Christmas-themed comic Donald's Homemade Christmas (first published in 2012), alongside Hortense, Matilda and Downy.