A lightbulb appearing above someone's head meaning “I have a great idea” is because, A) a bright image like a lightbulb is a metaphor of a bright idea, a good and smart idea. ... So when someone has a bright idea, they're having an Edison moment, like Edison's bright idea of the bright lightbulb.
The Prologue does not merely set the scene of Romeo and Juliet, it tells the audience exactly what is going to happen in the play. ... But the Prologue itself creates this sense of fate by providing the audience with the knowledge that Romeo and Juliet will die even before the play has begun. The prologue introduces the theme of fate when the lovers are called star-crossed and death-marked . This means that the events of their lives, and their deaths, are somehow already decided. There are lots of incidences throughout the play when the main characters refer to omens that hint at their tragic ending. William Shakespeare cleverly keeps tension in Romeo and Juliet by going immediately into the play, in the prologue he summarises the whole play, including the fact that Juliet a Capulet and Romeo a Montague are the lovers and that they die but the tension is kept because he does not say how the lovers die and that .
