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Samuel Clemens hears Data tell Guinan about "The Enterprise". In reality, Clemens aka Mark Twain wrote for a newspaper called "The Territorial Enterprise", often referred to simply as "The Enterprise", before moving to San Francisco in the 1860s.
According to production designer Richard D. James, a museum loaned out a horse-driven fire vehicle for the first time ever, thanks to the power of the words "Star Trek."
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.
Towards the end, Captain Picard mentions that "Samuel Clemens will write the books he was to have written after our encounter". Indeed, Clemens aka Mark Twain wrote seven books after 1893; the last one (The Mysterious Stranger) was published posthumously in 1916.
This two-parter is special for the amount of time Whoopi Goldberg was allotted to star in it. Normally available for only a day, she was more than happy to do several.