On a few occasions, there is a fourth nephew that appears, slipping through by a mistake of the artist. He has been named "Phooey Duck" by Disney comic editor Bob Foster. One short Egmont-licensed Disney comic explained Phooey's sporadic appearances as a freak incident of nature.
The boys are noted for having both identical appearances and personalities in most appearances, with the three sometimes shown as finishing each others' sentences as a running joke. In the theatrical shorts, Huey, Dewey, and Louie would often behave in a rambunctious manner, sometimes committing retaliation or revenge on their uncle Donald for something he did to them. In the comics, however, as developed by Al Taliaferro and Carl Barks, the boys usually are shown in a more well-behaved manner, usually helping their uncle Donald and great-uncle Scrooge McDuck in the adventure at hand. In the early Barks comics, the ducklings were still wild and unruly, but their character improved considerably due to their membership in the Junior Woodchucks and the good influence of their wise old great-grandmother Elvira Coot "Grandma" Duck.
Huey, Dewey, and Louie can in some cases be told apart by the color of their ball caps and sweaters or clothing: In DuckTales and Quack Pack, Huey is dressed in red, Dewey in blue, and Louie in green. In Egmont's comic publications, Huey is sometimes dressed in blue, Dewey in green and Louie in red. Usually they are colored randomly, though, and in some cases there have been yellow or orange nephews. In one cartoon (Donald's Happy Birthday, 1949), all three nephews wore red. Disney's archivist Dave Smith, in "Disney A to Z," said, "Note that the brightest hue of the three is red (Huey), the color of water, dew, is blue (Dewey), and that leaves Louie, and leaves are green."
They later starred in the 1987 animated television series DuckTales, in which they appeared in adventures with their great-uncle, Scrooge McDuck (Donald having enlisted in the U.S. Navy). The boys' personalities in this series were mainly based on their comic book appearances versus the theatrical shorts.
In 1990, the boys also made an appearance in the anti-drug TV special Cartoon All-Stars to the Rescue.
Huey, Dewey, and Louie also starred in the 1990s series Quack Pack, in which the three were portrayed as teenagers, and their names were given as Hubert, Deuteronomy and Louis Duck. In Quack Pack, the boys were given distinct personalities, with Huey serving as the group's leader, Dewey as a computer whiz, and Louie as enjoying sports.
Clarence Nash, Donald's voice actor, gave the voices to the boys in the cartoon shorts, making them just as unintelligible as Donald's. Huey, Dewey, and Louie were all voiced by Russi Taylor in DuckTales. In Quack Pack, they were voiced by Jeannie Elias, Pamela Segall, and Elizabeth Daily, respectively. Tony Anselmo voiced the characters in House of Mouse and Mickey Mouse Works, but Russi Taylor still voices the trio in other projects, such as the video games Donald Duck: Goin' Quackers and Mickey's Speedway USA, and the direct-to-video films Mickey's Once and Twice Upon a Christmas.
In Disney comic writer Don Rosa's (unofficial) continuity, Huey, Dewey, and Louie Duck were born around 1940 in Duckburg. True to his jocular style, Rosa occasionally makes subtle references to the untold mystery of the three boys' life: What became of their parents? In his epic comic series, Life and Times of Scrooge McDuck, Rosa pictures how Scrooge first met Donald and his nephews, saying: "I'm not used to relatives, either! The few I had seem to have... disappeared!" Huey, Dewey, and Louie answer: "We know how that feels, Unca Scrooge!"
In Some Heir Over the Rainbow, Huey, Dewey, and Louie, along with Donald Duck and Gladstone Gander, are tested by Scrooge McDuck, who wants to pick a heir to his fortune. Using the legend of gold at the end of rainbow, Scrooge secretly gives US$ 3,000 (One thousand to Huey, Dewey, and Louie, another for Gladstone, and the last one for Donald). Donald uses his money for a down payment of a new car, now being $1,000 in debt. Gladstone, considering himself too lucky to need the money this soon, hides the money for when and if he needs it, causing Scrooge to consider him a better option than Donald. Huey, Dewey, and Louie lend their money to a man who claims to need the money to search for a treasure. Initially thinking they were tricked out of the money, Scrooge actually considers leaving his fortune to Gladstone, even though he sees that as "an awful injustice to the world", but the man actually finds the treasure and pays the kids back. Scrooge makes Huey, Dewey, and Louie his heirs. Although this is disregarded in a number of later comics, it seems to be the most solidly canon indication of Scrooge's plans.