McDuck's creator Carl Barks started early, writing stories that centered on his favourite protagonist's uncle. This tradition was continued by numerous European cartoonists, and brought back to the United States by Keno Don Rosa. Many characters in their stories have never appeared in Donald Duck stories.
Most of the characters listed below have appeared in the 1980s Disney cartoon series DuckTales. Disney's Darkwing Duck series is nominally set in the DuckTales universe, in a metropolis called St. Canard, although sharing the denizen Launchpad McQuack, and a few crossover episodes involving Gizmoduck, there is no interaction. The Darkwing Duck material does not appear in Barks' comics.
However, in the magazine Disney Adventures, there was a five-part crossover/storyline titled "Legend of the Chaos God" which began with TaleSpin, and continued with Chip 'n Dale: Rescue Rangers, Goof Troop, and DuckTales, then concluded with Darkwing Duck.
For a more detailed listing, see List of characters from the Scrooge McDuck universe