Samuel Clemens expresses an interest in Halley's Comet. This body was visible in the sky both on the day of Mark Twain's birth in 1835 and the day of his death in 1910. There is a legend that he expected his own death to come in that year for that reason.
Producer Ronald D. Moore regretted that more was not done with the 1890s period. It had to be dropped due to time and budget constraints. Originally, they were supposed to be in 1893 for several months. They would meet at a café, run by Picard, with a running joke about how bad his food was.
The doctor in the hospital makes a comment of there not being an earthquake in the area for 30 years. In fact, the 1906 earthquake of San Francisco, which destroyed 3/4 of the city, would strike 13 years later, making it one of the worst natural disasters in United States history.
Samuel Clemens refers to "A Connecticut Yankee in King Arthur's Court", which was published in 1889, four years before the episode's time setting. This book inspired the 1998 movie "A Knight in Camelot" starring Whoopi Goldberg. This book is also referenced in the Voyager episode "Spirit Folk" in which Kathryn Janeway gives a copy of said book to the holodeck character of Michael Sullivan.
Towards the end of the episode, Captain Picard mentions that "Samuel Clemens will write the books he was to have written after our encounter". Indeed, Clemens wrote seven books after 1893; the last one (The Mysterious Stranger) was published posthumously.
Van Epperson has appeared in three Star Trek spin-off series. His first Star Trek appearance, as a morgue attendant in TNG "Time's Arrow, Part II" was deleted from the final version but he is still credited in the ending crawl. His second Star Trek appearance was a Bajoran clerk in charge of the station's assay office in DS9 "Q-Less". In his third Star Trek appearance, he played a "burlesque show alien" (credited as Alien Man) in Enterprise "Broken Bow".
This episode won two Emmy Awards. Only four other episodes of Trek have won this many. It won for Outstanding Individual Achievement in Costume Design for a Series (Robert Blackman) and Outstanding Individual Achievement in Hairstyling for a Series. It was also nominated for Outstanding Individual Achievement in Sound Editing for a Series.
Samuel Clemens hears Data tell Guinan about "The Enterprise". In reality, Clemens/Twain wrote for a newspaper called "The Territorial Enterprise", often referred to simply as "The Enterprise", before moving to San Francisco in the 1860's.
The trivia items below may give away important plot points.
In "Booby Trap", Guinan told Geordi La Forge she was attracted to bald men, because, long ago, one was very kind to her. In "Ensign Ro", Guinan tells Ro Laren that an old man helped her (Guinan) out when she was in serious trouble. Both references are seen here when Picard saves her life in the 19th century.
In the original script, Guinan claimed to be from a well-known Boston family, and that she was a close relative of Judge Truman Williams. Samuel Clemens checked her story, and received a telegram from Williams who had never heard of Guinan.