A tragedy written by William Shakespeare that tells the story of a young prince who becomes obsessed with getting revenge on his uncle, who murdered his father, the King of Denmark, and married his mother. It's famous for its themes of madness, caused by grief and a need for vengeance, as well as its oft-quoted lines, "to be or not to be, that is the question" and "alas, poor Yorick, I knew him, Horatio" (the latter is often misquoted as "alas, poor Yorick, I knew him well").
In the opening wraparound segment, the Crypt keeper says "zombie or not zombie?", this is a reference to the line "to be or not to be?" from act three, scene one of the play.