Brain Snacks: Tasty Tidbits of Knowledge
Shakespeare fathered twins, Judith and Hamnet (who died at age 11). This may have fueled his interest in twinning, in plays like Twelfth Night and The Comedy of Errors. (Source)
All Shook Up, a "jukebox musical" featuring Elvis Presley tunes, is based on the plot of Twelfth Night.