In Elizabethan England, the legal age for marriage (with parental permission) was twelve-years-old for girls and fourteen-years-old for boys. Nowadays, we tend to think of Juliet as just a tad young for nuptials (she's only thirteen in the play). (Source)
Since women weren't allowed to perform on the Elizabethan stage, Romeo and Juliet was originally played by an all-male cast. Female roles were most often played by young, pre-pubescent boys with high-pitched, "feminine" voices. Juliet would have been played by a boy until the late 1600s, when it first became acceptable for women to appear on the English stage. (source)
In 2008, Washington D.C.'s Shakespeare Theater Company staged a historically accurate, all-male performance of Romeo and Juliet. In response, D.C.'s Taffety Punk Theater Company staged an all-female production of the play and boasted that their version was "an hour shorter, a fraction of the cost, and [had] 100 percent more women."
It's often hard for a modern audience to picture Juliet as a thirteen-year-old girl. Actresses who play Juliet are usually much older. But one of the most successful productions of Romeo and Juliet ever—Franco Zeffirelli's 1968 film—cast fifteen-year-old Olivia Hussey as Juliet. Hussey won awards for her portrayal of Juliet, and her age was crucial to the role. At times, the actress looked like a little girl—way too young to attract Romeo's notice. At other moments, she looked like an incredibly attractive woman. Hussey captured the sense of Juliet's being right on the edge of maturity, and growing up through the experience of first love.
Disney's 2006 High School Musical, a film that features two teenage lovebirds who belong to feuding high school cliques, is considered a loose adaptation of Romeo and Juliet's forbidden love story. (Source)
The legal age of consent for marriage in Shakespeare's time may have been 12 for girls, but that doesn't mean that 12 year olds were getting married right and left. In fact, people got married relatively late in the 16th and 17th centuries—mostly around the mid-twenties for women and late twenties for men. (source)
Think Romeo's "O she doth teach the torches to burn bright" speech is an awesome pick-up line? So did John Gaugh, the author of a 17th century version of "Dating for Dummies." In his 1639 book, The Academy of Compliments, Gough "borrows" Romeo's lines and places them in a poem he calls "Encomiums on the Beauty of his Mistress." You can compare Romeo's lines to Gough's poem (courtesy of the Folger Shakespeare Library). We should note that plagiarism wasn't really a big deal back then. Even Shakespeare did it.
In the movie Shakespeare in Love (1998), Will Shakespeare (played by Joseph Fiennes) is in the middle of writing an awful play, Romeo and Ethel the Pirate's Daughter, when he falls in love with "Viola" (played by Oscar winner, Gwyneth Paltrow), who inspires him to pen Romeo and Juliet as we now know it.
Author Stephenie Meyer says that, in New Moon, Shakespeare's Romeo and Juliet is "really the theme of the novel." Our thoughts? The whole "missed connection" aspect to the plot doesn't really hold up in an era when all Edward would have had to do is make one quick phone call (or text message!) to see if Bella is still alive.