When Ratliff tells the story of how Clarence Snopes' political campaign ended ingloriously in "By the People" and again in The Mansion, he invents this man who plays the dirty trick on Snopes to hide himself behind. In the story he calls this "feller" a "low-minded rascal," an "underhanded son of a gun" and a "low-minded scoundrel" (138). In the novel he refers to him as an "anonymous underhanded son-of-a-gun" and an "underhanded feller" (349). In neither text, however, does Ratliff fool his listeners - or, almost certainly, any of Faulkner's readers.
This entry represents the "somebody" who gets a car in both "By the People" and The Mansion and then (as "they" in the short story and as "somebody" in the novel) drives Clarence Snopes home to get a dry pair of pants.
This "somebody" who gets a car and the "they" who drive Snopes home to get a dry pair of pants are a hard character or characters to bring into focus (138). We are assuming that it is probably one person.
"The owner of the car" in which Clarence Snopes takes refuge from the dogs is apparently not one of the "they" who drive the Senator home and "fetch [him] a pair of dry britches" (349).
This army officer - referred to as the "exec" in Devries' unit in Korea in "By the People" (134) and as the "second" in Devries' unit on a World War II battlefield in The Mansion (339) - is the executive officer who is second in command of the Negro combat unit that Devries commands. It's likely Faulkner imagined him as 'white': historically, as an officer, he would definitely have been white during World War II, and probably white in the Korean War.
In The Mansion this army nurse, "kin" to a Jefferson family, comes to Jefferson after the end of World War I as the town's "first female hero," having served as a lieutenant on a base hospital in France "within sound of the guns behind Montdidier" (199).
In "By the People" she serves in a field hospital in Korea, and helps Devries reward the soldier who saved him on the battlefield. In The Mansion she performs the same action in a field hospital somewhere else, during World War II.
In "By the People" and again in The Mansion this officer pins a medal on Devries; in the story it's for his heroism during the Korean War; in the novel, during World War II.
According to the narrator of "By the People," the compact organs manufactured by "the Remish Musical Company of South Bend, Indiana," were so popular with the country folk in Frenchman's Bend that in time "boy children from that section were bearing into puberty and even manhood Remish as their Christian names" (87). The narrator of this story is not noticeably facetious, and Faulkner's country people in other stories name their children things like "Montgomery Ward," so there's no reason to think this is just a joke.