1 Ophelia: Will, you have to get a grip on yourself. Time travel is a fantasy! You can't go back and talk to Tolkien about his book.
2 Ophelia: And it's his book. If you write a prequel, it's not really your own creative work. You have talent! Write something original!
2 Shakespeare: You're right, Ophelia.
3 Shakespeare: You've inspired me to write a tale of two households, both alike in dignity, from forth whose loins a pair of star-cross'd lovers take their life.
4 Mercutio: She said original.

Just to be clear, in this timeline/universe/whatever, Shakespeare was not an Elizabethan-era playwright. Romeo and Juliet does not exist.

Mercutio's comment is a comment on the prevalence and clichéd status of tragic love stories in general, especially given that Romeo and Juliet wasn't even the first such story in our own timeline. Our Shakespeare borrowed the basic plot from even earlier works - several of which existed before his time, at least as far back as Pyramus and Thisbe of ancient Roman times. And even the name of the play comes from an earlier work, The Tragical History of Romeus and Juliet, itself an English translation of an earlier Italian work named Giuletta e Romeo, which itself existed in multiple different versions of the same story by multiple authors of 16th century Italy!