Horatio is a true friend to Hamlet. He keeps Hamlet's confidences and tries to help him with his troubles. He genuinely cares about Hamlet as evidenced by his attempt to drink poison when Hamlet is dying. Hamlet begs Horatio not to kill himself, but to tell his story when he is dead. Horatio follows Hamlet's wishes and begins to tell Fortinbras the story of Hamlet's demise. Rosencranz and Guildenstern are false friends of Hamlet. They are willing to spy on their friend for the sake of money. Claudius must sent for them, while Horatio arrives on his own to attend the funeral of Hamlet's father. Rosencranz and Guidenstern keep reporting to Claudius and end up being messenger boys who carry a message that will bring Hamlet's death. Thus, they cannot be trusted and Hamlet knows this. That is why is constantly makes fun of them.