Bill Murray Reads Huck Finn

As the video explains, the section being read was not in the novel originally, but was added in some a critical edition in the 1990s.  If you're wondering why you've never heard of this, it's probably because it aired on CSPAN-2 in 1996.  Murray's reading ends about 14 minutes into the video.  It is followed with a panel discussion including William Styron (The Confessions of Nat Turner, Sophie's Choice), and authors Shelby Foote, Roy Blount, and Twain biographer Justin Kaplan.

Alternate World Encyclopedias

Arguably his most famous story, Jorge Luis Borges’s Tlön, Uqbar, and Orbis Tertius is about an encyclopedia of a non-existent world.  The encyclopedia in his story is so complete that it starts to supplant reality.  While the following have remained fictional (as far as we know), they are no less amazing.    

The Voynich Manuscript:  

Presumably dating from the 15^th century, the Voynich Manuscript is written in an unknown (or maybe indecipherable) language.  It is filled with illustrations of non-existent plants and astronomical charts.    

Named after the book dealer who brought it to popular attention in 1912, the Voynich manuscript is believed to have been passed down through history, at one point being bought by Emperor Rudolf II of Austria.  To this date, no one has been able to decode the manuscript, or for that matter, determine whether or not there is even anything to decode.

Codex Seraphinianus:

Created between 1976 and 1978 by the Italian painter, Luigi Serafini, the Codex Seraphinianus is an encyclopedia in surrealist style, containing what may or may not be an intelligible language.  Perhaps the most amazing detail is the mindblowing images. 

If you want your own copy, it’ll probably run you somewhere in the area of at $500.

The works of J. R. R. Tolkien:

People know  Tolkein as the author of the Lord of the Rings trilogy and the Hobbit.  It’s common knowledge that he created complete languages for the various races that populate Middle Earth.  But more than that, Tolkein created a complete world history.  In fact, between 1983 and 1996, Tolkein’s son edited and published twelve volumes of Middle Earth’s history, not counting the Silmarillion.

Thousands upon thousands of pages detailing the history, mythology, and languages of a world that never existed.