Hamlet
Hamlet is at first not sure whether to believe the ghost, so he tries to investigate. He pretends to be mad to hide what he is doing. As the play goes on, it becomes hard to tell if Hamlet is actually mad or still just pretending. His behaviour causes him to fall out with Ophelia, a girl he was in love with. He eventually has the idea of getting some actors to put on a play about a king being killed, in the same way that the ghost described, to see how Claudius reacts. Claudius panics when he sees the play, and Hamlet sees this as proof that his uncle is a murderer.