On the birthday card Sophie gave to Kevin as a child and later in the contacts on Kevin's phone, her name is spelled "Sophie," but in the note she gave to Kate on the napkin in The Pool (2016) (and seen again in this episode during Kate's flashback montage) her name is spelled "Sofie."
Toby states that he "went to a dinner party once with the guy who came in eighth on Carrie Underwood's season of Idol." That would be the fourth season of American Idol in which the eighth-place contestant was Nadia Turner, a woman, not a man.