San Serriffe is a fictional island nation created by The Guardian for April Fools' Day 1977 as an elaborate seven-page hoax supplement featuring puns related to printing terminology. The hoax became one of the most famous of the 20th century, spawning a substantial body of secondary literature and inspiring numerous reprises and cultural references.
A computer scientist describes receiving two reward checks from Donald Knuth over twenty years for finding errors in his books, including one in "Computer Modern Typefaces" on the first page and another erroneous submission that Knuth partially credited anyway.