Donald Ronald Douglas (Saul Rubinek) is Niles' divorce lawyer and, for a period, Daphne's boyfriend and fiancé. Ironically, despite his intense crush on Daphne, it is actually Niles who first introduces the two; they meet during Niles' divorce proceedings, while Donny, who is representing Niles against Maris, is helping Frasier to prepare his upcoming testimony. Although a highly successful lawyer, Donny is exceedingly boorish and brash (his antics include arriving for a meeting with Frasier and Niles in a tracksuit after a jog, and changing into his suit in front of them), and are anathema to Frasier's and Niles' refinement; his degree from the University of Las Vegas leads Yale/Cambridge-educated Niles to comment that there could have been "no problem finding tassels for those mortarboards", and although Harvard/Oxford-educated Frasier tells him to "stop being such a snob", his opinions are evidently similar. Their opinion of Donny changes when he cows a supposedly tough lawyer over the phone, greatly reducing the time Niles must wait for his day in court. Donny wins a favorable divorce settlement for Niles through his discovery that Maris' family fortune was based on urinal cakes; Niles' joy is immediately cut short when Donny starts dating Daphne.
Ultimately, Daphne leaves Donny at the altar in favor of Niles. Embittered, Donny initially sues both her and Frasier (who was responsible for Daphne and Niles getting together), but eventually drops the lawsuit. Daphne later encounters Donny in the final minutes before his court-room wedding to his new fiancée. In a later episode, he reappears with yet a different fiancée at Daphne's courtroom wedding with Niles.