When Rosencrantz and Guildenstern first arrived at Elsinore back in Act 2, scene 2, Hamlet asked them what brought them to Denmark, and they were not really forthcoming in their answer. First, Rosencrantz says that they have come "To visit [Hamlet], [...] no other occasion" (2.2.292). Hamlet doesn't believe them, however, and says, "I know the good king and queen have sent for / you" (2.2.303–304). Rosencrantz and Guildenstern seem to quickly confer with one another, and Guildenstern admits that they were, in fact, sent for. From here on out, Hamlet really cannot trust his old friends because first, they tried to lie to him, and second, he knows that they are reporting on his behaviors to his uncle.

Later, when Rosencrantz and Guildenstern ask Hamlet why he treats them with such distrust, he uses the metaphor of the recorder, a relatively simple musical instrument, to ask them why they think they can manipulate him and get information out of him when they are not even savvy enough to play the recorder and get the right notes. He suggests that they believe that he is actually more simple to control than the recorder. Hamlet absolutely believes that Rosencrantz and Guildenstern are loyal to Claudius now rather than himself.

After he kills Polonius, Hamlet does say that Rosencrantz is like a sponge "that soaks up the King's countenance, / his rewards, his authorities" (4.2.15–16). He is angry at his former friend for collaborating with his uncle/stepfather and seems to believe that Rosencrantz must be getting some kind of reward for spying on Hamlet at Claudius's request. He also believes that, once Rosencrantz has done what Claudius wants, Claudius will "squeeze" him "dry again" (4.2.21).