Executive Meddling: About a hundred years after Shakespeare died, an English theatre impresario (probably Colley Cibber) added an extra "witches" scene to Act III which was later assumed to have been part of the original play. (After the witches' "double, double, toil and trouble" speech, Hecate and three other witches show up randomly, sing a song called "Black Spirits", and vanish). This is never mentioned again. Most versions of the play produced before about 1970 include this scene; most since leave it out.
Hey, It's That Guy!: The RSC production filmed for television in 1979 is known universally as the nerd-tastic production. Why? Because...
Also the Roman Polaski version: Macbeth was played by Jon Finch who was first choice for Doyle in The Professionals. Banquo was played by Martin Shaw who DID play Doyle!
Cultural Translation: A 1970 Zulu-language adaptation by South African playwright Welcome Msomi, called uMabatha, adapts the play into Zulu tribal culture of the early 19th century (around the reign of the famous King Shaka). Theater critic Peter Ustinov remarked that until reading uMabatha, he did not understand Macbeth. Nelson Mandela remarked on the similarities between Macbeth and King Shaka.