Cassandra has just one song on her iPod playlist: R.E.M.'s "It's the End of the World as We Know It." She's the play's official crazy doomsday prophetess. (You know, the one nobody takes seriously.)
According to other sources, the god Apollo gave her the gift of prophesy but later got mad and was all "Oh, by the way, nobody's ever going to believe you when you tell them about the future." Shakespeare doesn't come out and say this but he sort of expects his audience to know the 411 on Cassandra. This explains why the men in her family don't take her seriously when she runs into the room, ranting and raving about how Troy's totally going to burn if they don't give Helen back to the Greeks ASAP:
Cry, Trojans, cry! practise your eyes with tears!
Troy must not be, nor goodly Ilion stand;
Our firebrand brother, Paris, burns us all.
Cry, Trojans, cry! a Helen and a woe:
Cry, cry! Troy burns, or else let Helen go. (2.2.108-112)
Of course, the audience knows that she's right, which makes it so ironic when her dad and brothers blow her off and say that nobody should pay attention to her "brain sick raptures." Every time she enters a room they're all Oh, boy, here comes our nutty sister again. Check it out:
What noise? what shriek is this?
'Tis our mad sister, I do know her voice. (2.2.98-99)
We don't really like to play Monday Morning Quarterback, but we're thinking that Troilus and his brothers probably should have paid attention to Cassandra's warnings. But that's just the way things go in this play.