Pretty much everyone in an English-speaking country with some formal education has probably heard of William Shakespeare or read one of his plays. After years of archeology, preservation, and transcripts, one can be fairly sure of the accuracy of most texts today. Interestingly enough, the people living in England around the late seventeenth century did not have this assurance.
(word of warning, for those who haven't read King Lear yet, there will be spoilers).
It seems that around 1687, a poet named Nahum Tate read Shakespeare's King Lear and didn't like the way it ended. Therefore, he wrote an entirely new ending, stuck it on to the end of the original play, and tried to set that up as the original play. Apparently, audiences believed it, and it took some years before someone found a copy of the original play and exposed Tate as the author of the revised version.
