Marcellus is one of the castle sentries in Shakespeare's Hamlet . He has a very small, but vitally important role. He is among the first to see the Ghost of Hamlet's Father walking the castle ramparts, and he goes with Bernardo, another sentry, and Horatio to tell Hamlet about the Ghost. It is he and Horatio who try to stop Hamlet from talking alone with the Ghost, in the fear that Hamlet may either die or go insane. Marcellus utters one of the most famous lines in the play: Something is rotten in the state of Denmark, sometimes misquoted as There's something rotten in Denmark .