William Shakespeare is without argument the most recognizable, famous playwright in the English language, and for good reason. His words, rich and dense in their poetry, tickle the academic sensibilities, while his still-relevant portrayals of humanity touch the hearts of readers and audiences alike. And of course when it came to sex jokes, no one wrote them better.
Shakespeare realized sexual jokes, especially double entendres, like no one else. He is never crude but he always reminds us of our humanity on every level. Now, of course, Shakespeare was not straight-up writing porn (his most explicit play, Henry VI, Part II, contains a total of just six kisses). He used his gift for wordplay to weave some clever sexual imagery and naughty puns into every play.
At the beginning of Shakespeare’s Romeo and Juliet, Romeo is feeling blue, lonely and his sex life is as dull as an afternoon of golf, or the US State of Nevada. And as he laments this fact, his friend Mercutio shares a rather odd suggestion with Romeo:
Romeo and Juliet (Act II Scene i)
‘If love be blind, love cannot hit the mark.
Now will he sit under a medlar tree,
And wish his mistress were that kind of fruit,
As maids call medlars when they laugh alone.
O Romeo! that she were, O! that she were
An open et caetera, and thou a poperin pear!’
– Reed International Books Ltd. 1992. The Illustrated Stratford Shakespeare London, Great Britain: Chancellor Press (1996) p. 708
Mercutio is talking about the fruit of a medlar tree. In Elizabethan England, this was colloquially referred to as a so-called open arse, for reasons that can never be adequately explained.
What we do know for sure, however, is that there has never been such thing as a poperin pear; in fact, it’s another old-timey play on words. Separate poperin into its three syllables and you get an Elizabethan penis euphemism “pop ‘er in.”
Yes, that’s right. Mercutio is saying, “What you need, my friend, is a girl who does anal.”
“The plays are absolutely packed with filth, […] I’ve found more than a hundred terms for vagina alone.” – Héloïse Sénéchal
Knowledge Guild 
I’ve always been especially amused by this little repartee from Act III, Scene II of Hamlet – the court is assembling for the performance by the traveling players, and Hamlet chooses to sit by Ophelia:
Yes I am familiar with that one too! Great stuff.