Aside from Tom, Myrtle, and Nick, the other three characters in the apartment are Catherine (Myrtle's sister) and Mr. and Mrs. McKee. Of Catherine, Myrtle says, "She’s said to be very beautiful by people who ought to know." Nick describes her objectively, as he intends with all of his descriptions, owing to his pride in his own honesty:
The sister, Catherine, was a slender, worldly girl of about thirty, with a solid, sticky bob of red hair, and a complexion powdered milky white. Her eye-brows had been plucked and then drawn on again at a more rakish angle, but the efforts of nature toward the restoration of the old alignment gave a blurred air to her face.
Nick also notes that Catherine's bracelets jingled incessantly as she walked and she acted as though she owned the apartment, though she did not. Nick also caught Catherine in a lie or a misunderstanding. Catherine informed Nick that the only reason Tom hadn't left Daisy for Myrtle is because Daisy is Catholic and therefore divorce would be a problem. Nick remarks the "elaborateness" of this lie; Daisy is not Catholic.
Nick describes Mr. McKee as a pale, feminine man who was generally respectful to everyone. Mrs. McKee, according to Nick, was "shrill, languid, handsome, and horrible."
With the possible exception of Mr. McKee, who seemed ineffectual, Nick is amiable but doesn't really care for anyone at this party. He is only able to deal with Tom, Myrtle, Catherine, and Mrs. McKee because he is drunk. This is why he says he was drawn to and repulsed by these people: "I was within and without, simultaneously enchanted and repelled by the inexhaustible variety of life."