Donald Ronald "Donny" 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 the tenth season premiere, "The Ring Cycle", he reappears with yet a different fiancée, a woman named Bridgett, at Daphne's court-room wedding with Niles. Donny thanks Daphne, stating that she played a major role in his eventual happiness, as if she had not left him at the altar, he would not have met his ex-wife, who introduced him to his new bride to be. Donny then comments that he hopes Niles and Daphne will attend their wedding, to which Daphne, absentmindedly being polite, states the same thing, only for Donny to graciously accept her invitation. While it appears that he no longer harbors any resentment towards the couple, when Daphne states that she cannot marry Niles (as, unbeknownst to Donny, Bridgett, Frasier, Martin, and Gertrude, they eloped to Reno, Nevada a week before, and were about to be married for a third time, in order to appease Gertrude, who had missed their second wedding, which occurred in order to please Frasier and Martin), Donny is vindictive towards him, declaring "YES! I KNEW IT! Now you know what it's like to have the love of your life dump you at the altar! And good luck trying to find somebody as good, because she just ain't out there!". This shocks and insults Bridgett, who leaves, causing a distressed Donny to chase after her.