Samuel L. "Sam" Clemens was an American author, humorist, and occasional moralist in the late 19th century and early 20th century. He was most noted for his literary works written under the pseudonym Mark Twain.
In 1893, at the age of 58, Samuel Clemens was visiting San Francisco. Clemens knew Guinan during this time and they associated with some of the same people. By then he had become disenchanted and, while attending the same party as Guinan, he derided the romantic views that claimed Earth was created for the sole purpose of hosting Humankind.
A time-stranded Data crashed the event, believing Guinan had come back in time to find him. Clemens overheard part of their conversation and became convinced that Data had traveled to the past for nefarious reasons. (TNG: "Time's Arrow")
Clemens tried to relate his theories to a young reporter. He stalked Guinan and followed Data's movements, aided by Ches Whitley. He even paid Jack London, the bellboy, to open Data's room in the Hotel Brian where he witnessed his temporal transceiver; during their conversation he urged the bellboy to pursue his dreams and write about them. Not long after, Data and Guinan found him in the closet, and Clemens threatened that he would warn Humanity about the impending invasion.
After hearing about two people "vanishing" and some confrontation in a hospital, he traveled to the Presidio and invited the reporter along for the story of his life. Armed with a Colt .45, he confronted Captain Jean-Luc Picard and his command crew, determined to turn them in to the authorities. But then the Devidian couple arrived from a portal, Data was decapitated, and Clemens followed everyone into the portal, finding himself on Devidia II of 2369.
Clemens eventually ended up being transported to the USS Enterprise-D and took a tour of the ship. He was convinced by Counselor Deanna Troi that the future had many positive merits. When it was learned that the Devidian temporal rift would only allow one person to go through it in either direction one more time, Clemens was returned to his time to rescue Captain Picard trapped in the past. After a briefing, he returned to Market Street and reached the cave where Picard and Guinan remained trapped; he supplied Picard with the Devidian cane and instructions on how to activate the ophidian and return to the future.
As Picard and Clemens parted ways, Picard wished that time had allowed him to know Clemens better, while Clemens assured Picard that he could always read his books. With Picard having departed, Clemens took care of the injured Guinan until help arrived, and agreed to pay the bill that Picard had incurred at the boarding house where the away team had briefly lodged while in the city. When medical staff arrived to take Guinan to receive care, Samuel Clemens escorted her away and left his watch with Data's head to be found in five hundred years later… and for history to repeat itself. (TNG: "Time's Arrow, Part II")
Clemens was also credited with responding "Reports of my death have been greatly exaggerated" upon reading his prematurely printed obituary. This quote was paraphrased by Picard after his life-saving heart surgery in 2365, as "Any rumors of my brush with death are greatly exaggerated", (TNG: "Samaritan Snare") and also by Picard during a Borg attack in 2373 as "Reports of my assimilation have been greatly exaggerated". (Star Trek: First Contact) In addition, Kasidy Yates referred to her morning sickness in 2375 as "Reports of my death have been exaggerated… but not by much", (DS9: "What You Leave Behind") and in 2377 The Doctor said "The reports of my decompilation have been greatly exaggerated." (VOY: "Body and Soul")
A photograph of Clemens with Picard was displayed on a sideboard, next to a statue, in Picard's study in 2399. (PIC: "Maps and Legends") It was also displayed as part of a holographic reproduction of Picard's study aboard La Sirena. (PIC: "Absolute Candor", et al.)
Clemens was played by actor Jerry Hardin. His makeup for the role involved work by Doug Drexler. (Star Trek: Communicator issue 136, p. 31) With the encouragement of director Les Landau, Hardin recreated the role for a successful one-man stage show not long after the TNG episodes featuring him.
It is interesting to note that in 1893, Samuel Clemens was traveling on book tours, mostly in Europe. He only returned to the US briefly (New York City) and moved his family to Berlin, Germany. It is unlikely that he was in the San Francisco area at all.
Coincidentally, both his birth and death coincided with the passing of Halley's Comet, which he asked about aboard the Enterprise.
The books which Clemens completed, or wrote, after his 1893 encounter with the Enterprise included Pudd'nhead Wilson, Personal Recollections of Joan of Arc, The Mysterious Stranger, and his autobiography.
William Shatner played Mark Twain in "Marked Twain", an episode of the ninth season of Murdoch Mysteries. He was nominated for a Canadian Screen Award for his performance.