Charles tells Eliza, "I've even heard a rumor of two brothers in North Carolina who are working on a flying machine." Since he disappears the next day, December 18, 1903, he says this on the actual day of the Wright Brothers' first flights.
The three books Charles reads to research time travel are: The Time Machine, A Christmas Carol, and A Connecticut Yankee in King Arthur's Court.
Ryan Paevey and Nelson Wong appeared together in Christmas at the Plaza (2019) and Hope at Christmas (2018).